Subfamily Of Transcription Factors Research Articles

Epigenetic Suppression of the T-box Subfamily 2 (TBX2) in Human Non-Small Cell Lung Cancer.

(1) The TBX2 subfamily of transcription factors (TBXs 2, 3, 4 and 5) are markedly down-regulated in human non-small cell lung cancer (NSCLC) and exert tumor suppressor effects in lung malignancy. Yet, mechanisms underlying suppressed expression of the TBX2 subfamily in NSCLC are elusive. Here, we interrogated probable epigenetic mechanisms in suppressed expression of the TBX2 subfamily in human NSCLC. (2) TBX2 subfamily gene expression and methylation levels in NSCLC and normal lung tissues were surveyed using publicly available RNA-sequence and genome-wide methylation datasets. Methylation β-values of the four genes were statistically compared between NSCLCs and normal lung tissues, correlated with gene expression levels, and interrogated with clinicopathological variables. Expression and methylation levels of TBXs were quantified in NSCLC cells using real-time PCR and methylation-specific PCR assays, respectively. Effects of the DNA methyltransferase inhibitor 5-azacytidine (Aza) on TBX2 subfamily expression were assessed in NSCLC cells. Impact of TBX2 subfamily expression on Aza-treated cells was evaluated by RNA interference. (3) All four TBXs were significantly hypermethylated in NSCLCs relative to normal lung tissues (p < 0.05). Methylation β-values of the genes, with exception of TBX2, were significantly inversely correlated with corresponding mRNA expression levels (p < 0.05). We found no statistically significant differences in hypermethylation levels of the TBX2 subfamily by clinicopathological features including stage and tobacco history. Expression levels of the TBX genes were overall suppressed in NSCLC cells relative to normal alveolar cells. Members of the subfamily were significantly hypermethylated in all tested NSCLC cell lines relative to normal alveolar cells. Treatment with Aza induced the expression of the TBX2 subfamily concomitant with NSCLC cell growth inhibition. Further, simultaneous knockdown of the four TBX genes markedly reduced anti-growth effects of Aza in NSCLC cells. (4) Our study sheds light on new epigenetic profiles in the molecular pathogenesis of human NSCLC.

Ectopic expression of the AaFUL1 gene identified in Anthurium andraeanum affected floral organ development and seed fertility in tobacco

Anthurium andraeanum is a high-grade potted flower that enjoys global popularity. Its floral organs have been substantially modified, and its ornamental value is based on its petaloid bracts. MADS-box gene products are important transcription factors that control plant development. In particular, the APETALA1 (AP1)/FRUITFULL (FUL) family of MADS-box genes plays a key role in flowering transitions and out-whorl floral organ identity specification. In this report, one FUL-like gene was cloned from Anthurium andraeanum and named AaFUL1 after bioinformatics identification. Subsequent subcellular localization experiments confirmed that the AaFUL1 protein was located in the nucleus, and data obtained from an expression analysis indicated that the relative expression level of AaFUL1 was the highest in bracts and inflorescences, while its expression was relatively low in stems and roots. Next, an AaFUL1 overexpression vector was constructed and ectopically expressed in tobacco. The transformants did not show any early flowering phenotype, but the average internode length of the inflorescence branch was significantly higher than that observed in the control, and its petal color had substantially faded. The morphology of the petal and pistil was clearly changed, the fruit was deformed, and the seed was largely aborted. These data indicate that even though the sequence of AaFUL1 is relatively conserved, its function differs from that of other orthologs, and the FUL subfamily of MADS-box transcription factors may have taken on new functions during the evolution processes. The results of this experiment enrich our knowledge of FUL transcription factors in monocotyledon plants.

Insights from the crystal structure of the chicken CREB3 bZIP suggest that members of the CREB3 subfamily transcription factors may be activated in response to oxidative stress

cAMP response element binding Protein 3 (CREB3) is an endoplasmic reticulum (ER) membrane‐bound transcription factor, which belongs to the basic leucine zipper (bZIP) superfamily of eukaryotic transcription factors. CREB3 plays a role in the ER‐stress induced unfolded protein response (UPR) and is a multifunctional cellular factor implicated in a number of biological processes including cell proliferation and migration, tumor suppression, and immune‐related gene expression. To gain structural insights into the transcription factor, we determined the crystal structure of the conserved bZIP domain of chicken CREB3 (chCREB3) to a resolution of 3.95 Å. The X‐ray structure provides evidence that chCREB3 can form a stable homodimer. The chCREB3 bZIP has a structured, pre‐formed DNA binding region, even in the absence of DNA, a feature that could potentially enhance both the DNA binding specificity and affinity of chCREB3. Significantly, the homodimeric bZIP possesses an intermolecular disulfide bond that connects equivalent cysteine residues of the parallel helices in the leucine zipper region. This disulfide bond in the hydrophobic core of the bZIP may increase the stability of the homodimer under oxidizing conditions. Moreover, sequence alignment of bZIP sequences from chicken, human, and mouse reveals that only members of the CREB3 subfamily contain this cysteine residue, indicating that it could act as a redox‐sensor. Taken together, these results suggest that the activity of these transcription factors may be redox‐regulated and they may be activated in response to oxidative stress.

The phytochrome-interacting family of transcription factors in maize (Zea mays L.): identification, evolution, and expression analysis

The phytochrome-interacting factor (PIF) subfamily of transcription factors is among the most important families of plant transcriptional regulators. PIFs regulate multiple biological processes, especially the photomorphogenic development. However, studies on PIF are mostly concentrated in Arabidopsis, little information on PIFs in maize (Zea mays L.) is currently available. The release of assembled genome sequences of maize enables the genome-wide investigation of maize PIF proteins. In this study, six PIF genes in maize were identified and named ZmPIF1–6. Among them, ZmPIF1 and ZmPIF3 were previously cloned in our laboratory. According to the structural features of their proteins, maize PIF genes (ZmPIFs) were classified into two main groups. Group I have an active phytochrome B (APB) domain and interacts with ZmphyB1. Group II has APA and APB domains and interacts with ZmphyA1 and ZmphyB1. The global expression patterns of ZmPIF genes in various tissues, as well as response of ZmPIF genes to diurnal rhythm, environmental stresses, and plant hormones were analyzed. The expression patterns of the ZmPIF genes suggested that ZmPIF1 and ZmPIF3 play an important role in the diurnal rhythm, while ZmPIF4 and ZmPIF6 are possibly the genes that respond to stimulation during plant growth and development. Meanwhile, the functions of ZmPIF2 and ZmPIF5 requires further investigation. These results can facilitate the exploration of the role of maize PIF-mediated plant signaling pathways and contribute to the development of molecular breeding for maize.

Monitoring the Transcriptional Activity of FOXO Transcription Factors by Analyzing their Target Genes.

FOXO proteins represent a subfamily of transcription factors that belong to the forkhead family. The study of FOXO target genes can be performed using Real-Time PCR (RT-PCR). The RT-PCR is a sensitive method that allows the detection and quantification of minute amounts of nucleic acids. In RT-PCR the accumulation of the amplicon is detected and measured as the reaction progresses. Here, we describe the application of RT-PCR technique to monitor the transcriptional activity of FOXO transcription factors.

Bidirectional regulation of osteogenic differentiation by the FOXO subfamily of Forkhead transcription factors in mammalian MSCs.

Through loss‐ and gain‐of‐function experiments in knockout and transgenic mice, Forkhead box O (FOXO) family transcription factors have been demonstrated to play essential roles in many biological processes, including cellular proliferation, apoptosis and differentiation. Osteogenic differentiation from mesenchymal stem cells (MSCs) into osteoblasts is a well‐organized process that is carefully guided and characterized by various factors, such as runt‐related transcription factor 2 (Runx2), β‐catenin, osteocalcin (OCN), alkaline phosphatase (ALP) and activating transcription factor 4 (ATF4). Accumulating evidence suggests multiple interactions among FOXO members and the differentiation regulatory factors listed above, resulting in an enhancement or inhibition of osteogenesis in different stages of osteogenic differentiation. To systematically and integrally understand the role of FOXOs in osteogenic differentiation and explain the contrary phenomena observed in vitro and in vivo, we herein summarized FOXO‐interacting differentiation regulatory genes/factors and following alterations in differentiation. The underlying mechanism was further discussed on the basis of binding types, sites, phases and the consequent downstream transcriptional alterations of interactions among FOXOs and differentiation regulatory factors. Interestingly, a bidirectional effect of FOXOs on balancing osteogenic differentiation was discovered in MSCs. Moreover, FOXO factors are reported to be activated or suppressed by several context‐dependent signalling inputs during differentiation, and the underlying molecular basis may offer new drug development targets for treatments of bone formation defect diseases.

E26 transformation (ETS)‑specific related transcription factor‑3 (ELF3) orchestrates a positive feedback loop that constitutively activates the MAPK/Erk pathway to drive thyroid cancer.

Thyroid cancer is the most commonly diagnosed malignancy of the endocrine system, the incidence of which has increased rapidly in the last 30years. Genetic alterations in pathways, including the mitogen‑activated protein kinase (MAPK)/extracellular signal‑regulated kinase (Erk) and phosphatidylinositol‑3‑kinase (PI3K)/protein kinaseB (Akt) pathways, are the driving force behind the development of differentiated thyroid cancer cases into aggressive and undifferentiated forms of thyroid cancer. E26 transformation (ETS)‑specific related transcription factor‑3 (ELF3) belong to the epithelial‑specific subfamily of ETS transcription factors and has recently been reported to be involved in various pathophysiological processes. However, the role of ELF3 in thyroid cancer has not yet been investigated. In the present study, data from The Cancer Genome Atlas (TCGA) were analyzed, and it was revealed that ELF3 was overexpressed in patients with papillary thyroid cancer (PTC). Furthermore, the expression of ELF3 was found to be higher in thyroid cancer tissues with a B‑Raf proto‑oncogene (BRAF) mutation as determined by western blot analysis and IHC staining. Additionally, ELF3 overexpression predicted a poor prognosis in patients with PTC. The MAPK signaling pathway inhibitor PLX4032 was demonstrated to strongly attenuate ELF3 protein levels in BRAF‑mutant thyroid cancer cell lines. Knockdown of ELF3 with small interfering RNA (siRNA) inhibited the growth, clone formation, migration and invasion of BRAF mutant thyroid cancer cells. Mechanistically, ELF3 modulated the activity of the MAPK/Erk pathway via transcriptional regulation of the human epidermal growth factor receptor2 family of receptors as determined by RT‑qPCR. In conclusion, the present study demonstrated ELF3 to be a potential prognostic marker for patients with thyroid cancer. Notably, ELF3 was demonstrated to form a positive feedback loop with MAPK pathways leading to the progression of BRAF‑mutant thyroid cancer.

Nach Is a Novel Subgroup at an Early Evolutionary Stage of the CNC-bZIP Subfamily Transcription Factors from the Marine Bacteria to Humans.

Normal growth and development, as well as adaptive responses to various intracellular and environmental stresses, are tightly controlled by transcriptional networks. The evolutionarily conserved genomic sequences across species highlights the architecture of such certain regulatory elements. Among them, one of the most conserved transcription factors is the basic-region leucine zipper (bZIP) family. Herein, we have performed phylogenetic analysis of these bZIP proteins and found, to our surprise, that there exist a few homologous proteins of the family members Jun, Fos, ATF2, BATF, C/EBP and CNC (cap’n’collar) in either viruses or bacteria, albeit expansion and diversification of this bZIP superfamily have occurred in vertebrates from metazoan. Interestingly, a specific group of bZIP proteins is identified, designated Nach (Nrf and CNC homology), because of their strong conservation with all the known CNC and NF-E2 p45 subunit-related factors Nrf1 and Nrf2. Further experimental evidence has also been provided, revealing that Nach1 and Nach2 from the marine bacteria exert distinctive functions, when compared with human Nrf1 and Nrf2, in the transcriptional regulation of antioxidant response element (ARE)-battery genes. Collectively, further insights into these Nach/CNC-bZIP subfamily transcription factors provide a novel better understanding of distinct biological functions of these factors expressed in distinct species from the marine bacteria to humans.

Neglected Functions of TFCP2/TFCP2L1/UBP1 Transcription Factors May Offer Valuable Insights into Their Mechanisms of Action.

In recent years, the TFCP2 (transcription factor cellular promoter 2)/TFCP2L1 (TFCP2-like 1)/UBP1 (upstream binding protein 1) subfamily of transcription factors has been attracting increasing attention in the scientific community. These factors are very important in cancer, Alzheimer’s disease, and other human conditions, and they can be attractive targets for drug development. However, the interpretation of experimental results is complicated, as in principle, any of these factors could substitute for the lack of another. Thus, studying their hitherto little known functions should enhance our understanding of mechanisms of their functioning, and analogous mechanisms might govern their functioning in medically relevant contexts. For example, there are numerous parallels between placental development and cancer growth; therefore, investigating the roles of TFCP2, TFCP2L1, and UBP1 in the placenta may help us better understand their functioning in cancer, as is evidenced by the studies of various other proteins and pathways. Our review article aims to call the attention of the scientific community to these neglected functions, and encourage further research in this field. Here, we present a systematic review of current knowledge of the TFCP2/TFCP2L1/UBP1 subfamily in reproduction, embryonic development, renal function, blood-pressure regulation, brain function, and other processes, where their involvement has not been studied much until now.

A plant-responsive bacterial-signaling system senses an ethanolamine derivative

Certain plant-associated Proteobacteria sense their host environment by detecting an unknown plant signal recognized by a member of a LuxR subfamily of transcription factors. This interkingdom communication is important for both mutualistic and pathogenic interactions. The Populus root endophyte Pseudomonas sp. GM79 possesses such a regulator, named PipR. In a previous study we reported that PipR activates an adjacent gene (pipA) coding for a proline iminopeptidase in response to Populus leaf macerates and peptides and that this activation is dependent on a putative ABC-type transporter [Schaefer AL, et al. (2016) mBio 7:e01101-16]. In this study we identify a chemical derived from ethanolamine that induces PipR activity at picomolar concentrations, and we present evidence that this is the active inducer present in plant leaf macerates. First, a screen of more than 750 compounds indicated ethanolamine was a potent inducer for the PipR-sensing system; however, ethanolamine failed to bind to the periplasmic-binding protein (PBP) required for the signal response. This led us to discover that a specific ethanolamine derivative, N-(2-hydroxyethyl)-2-(2-hydroxyethylamino) acetamide (HEHEAA), binds to the PBP and serves as a potent PipR-dependent inducer. We also show that a compound, which coelutes with HEHEAA in HPLC and induces pipA gene expression in a PipR-dependent manner, can be found in Populus leaf macerates. This work sheds light on how plant-associated bacteria can sense their environment and on the nature of inducers for a family of plant-responsive LuxR-like transcription factors found in plant-associated bacteria.

MdMYB58 Modulates Fe Homeostasis by Directly Binding to the MdMATE43 Promoter in Plants.

Nutrient element deprivation, such as iron (Fe) deficiency stress, is a major factor limiting plant survival and proliferation in marginal soils. To cope with a low Fe environment, plants have evolved elaborate mechanisms underlying Fe homeostasis via intricate transcriptional and post-transcriptional regulation. Here, we characterized the Fe deficiency-inducible MYB transcription factor MdMYB58 in apple plants. Overexpressing MdMYB58 resulted in the accumulation of Fe in the root of transgenic Arabidopsis and apple calli when they were exposed to low Fe available conditions. Further investigation revealed that MdMYB58 bound to the promoter of MdMATE43, and its homolog FRD3 in Arabidopsis. Transient expression and stable transgenic assays in apple calli indicated that MdMYB58 transcriptionally repressed MdMATE43 mRNA, as well as FRD3 in Arabidopsis. Interestingly, AtMYB58, the homolog of MdMYB58, possessed higher binding activities to MdMATE43 and FRD3, which suggests a potentially conserved feature of MYB58 binding to MATE transporters in plants. Additionally, MYB-MATE-mediated regulation of Fe homeostasis may be related to the PYE-related Fe deficiency regulatory network via MdSAT1, a member of the IVa subfamily of bHLH transcription factors. Co-overexpression of MdSAT1 competitively weakened MdMYB58-overexpression induced repression of MdMATE43 transcript abundancy by protein-protein interaction. Taken together, the newly identified MYB-bHLH transcription factor expands our understanding of multilevel molecular mechanisms that plants use to coordinate Fe demand with Fe uptake, transport, and tissue partitioning under low Fe conditions.

The Tumor Suppressor CIC Directly Regulates MAPK Pathway Genes via Histone Deacetylation.

Oligodendrogliomas are brain tumors accounting for approximately 10% of all central nervous system cancers. CIC is a transcription factor that is mutated in most patients with oligodendrogliomas; these mutations are believed to be a key oncogenic event in such cancers. Analysis of the Drosophila melanogaster ortholog of CIC, Capicua, indicates that CIC loss phenocopies activation of the EGFR/RAS/MAPK pathway, and studies in mammalian cells have demonstrated a role for CIC in repressing the transcription of the PEA3 subfamily of ETS transcription factors. Here, we address the mechanism by which CIC represses transcription and assess the functional consequences of CIC inactivation. Genome-wide binding patterns of CIC in several cell types revealed that CIC target genes were enriched for MAPK effector genes involved in cell-cycle regulation and proliferation. CIC binding to target genes was abolished by high MAPK activity, which led to their transcriptional activation. CIC interacted with the SIN3 deacetylation complex and, based on our results, we suggest that CIC functions as a transcriptional repressor through the recruitment of histone deacetylases. Independent single amino acid substitutions found in oligodendrogliomas prevented CIC from binding its target genes. Taken together, our results show that CIC is a transcriptional repressor of genes regulated by MAPK signaling, and that ablation of CIC function leads to increased histone acetylation levels and transcription at these genes, ultimately fueling mitogen-independent tumor growth.Significance: Inactivation of CIC inhibits its direct repression of MAPK pathway genes, leading to their increased expression and mitogen-independent growth.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/15/4114/F1.large.jpg Cancer Res; 78(15); 4114-25. ©2018 AACR.

Xenopus SOX5 enhances myogenic transcription indirectly through transrepression

In anamniotes, somite compartimentalization in the lateral somitic domain leads simultaneously to myotome and dermomyotome formation. In the myotome, Xenopus Sox5 is co-expressed with Myod1 in the course of myogenic differentiation. Here, we studied the function of Sox5 using a Myod1-induced myogenic transcription assay in pluripotent cells of animal caps. We found that Sox5 enhances myogenic transcription of muscle markers Des, Actc1, Ckm and MyhE3. The use of chimeric transactivating or transrepressive Sox5 proteins indicates that Sox5 acts as a transrepressor and indirectly stimulates myogenic transcription except for the slow muscle-specific genes Myh7L, Myh7S, Myl2 and Tnnc1. We showed that this role is shared by Sox6, which is structurally similar to Sox5, both belonging to the SoxD subfamily of transcription factors. Moreover, Sox5 can antagonize the inhibitory function of Meox2 on myogenic differentiation. Meox2 which is a dermomyotome marker, represses myogenic transcription in Myod-induced myogenic transcription assay and in Nodal5-induced mesoderm from animal cap assay. The inhibitory function of Meox2 and the pro-myogenic function of Sox5 were confirmed during Xenopus normal development by the use of translation-blocking oligomorpholinos and dexamethasone inducible chimeric Sox5 and Meox2 proteins. We have therefore identified a new function for SoxD proteins in muscle cells, which can indirectly enhance myogenic transcription through transrepression, in addition to the previously identified function as a direct repressor of slow muscle-specific genes.

Abstract 5509: Early suppression of the TBX2 subfamily of transcription factors during in vivo tobacco carcinogen-mediated lung adenocarcinoma development

Abstract Targets for early treatment of lung adenocarcinoma (LUAD), the leading cause of cancer mortality among smokers, are far and few largely due to the paucity in our knowledge of the molecular pathogenesis of the malignancy. In our efforts to address this glaring gap in knowledge, we previously surveyed the expression of members of the T-box 2 subfamily of transcription factors (TBXs 2, 3, 4 and 5) in normal and malignant lung tissues owing to their evolutionarily conserved expression and function in normal lung organogenesis,. We found that all four members were profoundly suppressed in human premalignant lesions and malignant LUADs. While these findings showed that the TBX2 subfamily of transcription factors is suppressed in overt LUADs, their role in the molecular and temporal oncogenesis of the malignancy in smokers is still elusive. To fill this void, we first surveyed the expression of these genes in a mouse model of LUAD we had developed comprised of knockout of the airway-lineage specific gene Gprc5a (Gprc5a-/-) and exposure to the tobacco-specific carcinogen nicotine-derived nitrosamine ketone (NNK). We had previously found that NNK-exposed Gprc5a-/- mice developed adenomas and LUADs that harbored somatic activating mutations (p.G12D and p.Q61R) in the Kras oncogene – the same variants posited to function as drivers of LUAD in human smokers. In ongoing RNA-Seq efforts cataloging expression in frozen-fixed temporally collected (up to seven months post-NNK) Gprc5a-/- normal tissues, adenomas and LUADs, we found that all four TBX genes were markedly down-regulated (all P &amp;lt; 0.05) in all lesions and across all time points following exposure, relative to normal lung tissues. Concurrent analysis of canonical genes directly activated or repressed by the TBX2 subfamily were found to be consistently down-regulated or elevated, respectively, in the same NNK-exposed lung lesions relative to normal lung. We employed a mouse LUAD cell line (mF471 cells) we had previously derived from an NNK-exposed Gprc5a-/- mouse tumor to further functionally probe the role of TBX2 subfamily in LUAD oncogenesis. Transient over-expression of each of the four TBX2 subfamily members in the mF471 LUAD cells significantly inhibited cell proliferation and growth evidenced by trypan blue dye exclusion, MTT and cell cycle analyses. Over-expression of each of the four TBX2 subfamily members yielded similar anti-growth effects with significant increases in sub-G0 phase of the cell cycle indicating cell cycle arrest (up to 35%) 48 hours following transfection. These findings suggest that the TBX2 subfamily genes are suppressed at early stages in the development of smoking-associated Kras-mutant LUAD and play key tumor suppressor roles in the molecular pathogenesis of this common and fatal malignancy. Citation Format: Athar Khalil, Junya Fujimoto, Tina McDowell, Paul Scheet, Georges Nemer, Humam Kadara. Early suppression of the TBX2 subfamily of transcription factors during in vivo tobacco carcinogen-mediated lung adenocarcinoma development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5509.

Abstract 5513: Role of the evolutionarily conserved TBX2 subfamily of transcription factors in the molecular pathogenesis of human lung adenocarcinoma

Abstract T-box (TBX) transcription factors are evolutionary conserved genes and master regulators of transcription repression and activation. In mammals, 18 members were described functionally and structurally, of which the TBX2 subfamily (TBX2, TBX3, TBX4, TBX5) genes were shown to be expressed early on in the developing lung bud and tracheae. Despite these insights into the role of the TBX2 subfamily in normal lung organogenesis, little is known about the role of these genes in pathological pulmonary conditions in humans; particularly lung cancer, an aggressive malignancy that is the leading cause of cancer-deaths worldwide. To fill this void, our group previously surveyed the expression of TBX2 subfamily in various publicly available datasets and found that all four members were preferentially and highly expressed in human normal lung, but markedly and consistently suppressed in lung adenocarcinoma (LUAD) the most common histological subtype of lung cancer. We also showed that the subfamily was also suppressed in preneoplastic lesions preceding the development of LUADs. Following the above and to further elucidate the role of the TBX2 subfamily in LUAD pathogenesis, we first probed and confirmed abundant expression of protein products of the four members by immunostaining in adult human normal lung tissues. On the other hand, quantitative real-time PCR and western blotting analyses demonstrated overall suppressed expression of the genes and corresponding proteins in a panel of human LUAD cell lines. Transient over-expression of each of the four genes in human LUAD cell lines (H1299 and H1944) was found to overall significantly inhibit cancer cell growth and proliferation. Additionally, over-expression of the four genes induced apoptosis, evidenced by sub-G0/G1 accumulation following cell cycle analysis, in both cell lines (ranging from 40% to 90% compared to control). To understand genome-wide effects of TBX2 subfamily in LUAD, we interrogated global expression programs downstream of these transcription factors by RNA-Seq in H1299 cells engineered to over-express the four members separately. We unraveled novel signaling cues signifying canonical pathways found in our analysis to be directly regulated by members of the TBX2 subfamily. These included, among others, inhibition of cell cycle progression and glycolysis, suppression of pathways mediated by epidermal growth factor (EGFR) and WNT signaling and activation of the major anti-tumor immune marker interferon gamma (IFNG). All in all, our findings point to tumor suppressor roles for TBX2 subfamily in human LUAD pathogenesis and suggest “oncophenotypes” downstream of these factors as putative targets for lung cancer therapy. Citation Format: Athar Khalil, Nehme El-Hachem, Batoul Dekmak, Humam Kadara, Georges Nemer. Role of the evolutionarily conserved TBX2 subfamily of transcription factors in the molecular pathogenesis of human lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5513.

The Aborted Microspores (AMS)-Like Gene Is Required for Anther and Microspore Development in Pepper (Capsicum annuum L.).

Pepper (Capsicum annuum L.) is an economically important vegetable crop worldwide. Although many genes associated with anther and pollen development have been identified, little is known about the mechanism of pollen abortion in pepper. Here, we identified and isolated two putative aborted microspore (AMS) isoforms from pepper flowers: CaAMS1 and CaAMS2. Sequence analysis showed that CaAMS2 was generated by retention of the fourth intron in CaAMS1 pre-mRNA. CaAMS1 encodes a putative protein with a basic helix-loop-helix (bHLH) domain belonging to the MYC subfamily of bHLH transcription factors, and it is localized to the nucleus. Truncated CaAMS2-1 and CaAMS2-2 are produced by alternative splicing. Quantitative real-time PCR analysis showed that CaAMS (referred to CaAMS1 and CaAMS2-2) was preferentially expressed in stamens and its expression level gradually decreases with flower development. RNA in situ hybridization analysis showed that CaAMS is strongly expressed in the tapetum at the tetrad and uninucleate stages. Downregulation of CaAMS led to partial shortened filaments, shriveled, indehiscent stamens and abortive pollens in pepper flowers. Several genes involved in pollen exine formation were downregulated in defective CaAMS-silenced anthers. Thus, CaAMS seems to play an important role in pepper tapetum and pollen development by regulating a complex genetic network.

A mechanism involving sibling transcription factor assistance preserves the integrity of an active Foxp3 locus in peripherally induced regulatory T cells.

Abstract Regulatory T (Treg) cell mediated dominant negative regulation is critical for suppressing hyper-immune responses. Broadly classified as thymus derived (tTreg) and peripherally induced (iTreg), these cells share a stringent dependence on the transcription factor Foxp3. In spite of significant advances, precise understanding of the molecular events that promote and preserve unceasing expression of Foxp3 in Treg cells is still incompletely understood. Here we show that Foxp1, a forkhead transcription factor and thus a sibling family member of Foxp3, is essential for sustained high level expression of Foxp3 specifically in iTreg cells. By being readily associated with the Foxp3 locus in a TGFβ dependent manner, Foxp1 critically participates during multiple phases of iTreg development and maturity. By employing an inducible model of temporal deletion of Foxp1 in precursor CD4+ T cells, we found that it is required for optimum expression of Foxp3 during the onset of iTreg induction. Even a conditional ablation of Foxp1 in iTreg cells at a later developmental time point, when high level transcription of Foxp3 was already established, resulted in dramatic instability of the differentiated cell state. Accordingly, Treg specific deletion of Foxp1 renders cells gradually lose Foxp3, resulting in dramatically reduced Nrp1−Helios− iTreg compartment in mice, ensuing significantly augmented intestinal inflammation. Interestingly, the stability of Foxp3 expression in tTreg cells remained unaffected in the absence of Foxp1. Thus, our study unravels a mechanistic module of evolutionarily akin members of a transcription factor subfamily in establishing a novel molecular program indispensable to ensure efficient immune homeostasis.

The AP2/ERF transcription factor CmERF053 of chrysanthemum positively regulates shoot branching, lateral root, and drought tolerance.

We find that the DREB subfamily transcription factor, CmERF053, has a novel function to regulate the development of shoot branching and lateral root in addition to affecting abiotic stress. Dehydration-responsive element binding proteins (DREBs) are important plant transcription factors that regulate various abiotic stresses. Here, we isolated an APETALA2/ethylene-responsive factor (AP2/ERF) transcription factor from chrysanthemum (Chrysanthemum morifolium 'Jinba'), CmERF053, the expression of which was rapidly up-regulated by main stem decapitation. Phylogenetic analysis indicated that it belongs to the A-6 group of the DREB subfamily, and the subcellular localization assay confirmed that CmERF053 was a nuclear protein. Overexpression of CmERF053 in Arabidopsis exhibited positive effects of plant lateral organs, which had more shoot branching and lateral roots than did the wild type. We also found that the expression of CmERF053 in axillary buds was induced by exogenous cytokinins. These results suggested that CmERF053 may be involved in cytokinins-related shoot branching pathway. In this study, an altered auxin distribution was observed during root elongation in the seedlings of the overexpression plants. Furthermore, overexpress CmERF053 gene could enhance drought tolerance. Together, these findings indicated that CmERF053 plays crucial roles in regulating shoot branching, lateral root, and drought stress in plant. Moreover, our study provides potential application value for improving plant productivity, ornamental traits, and drought tolerance.

Heterologous expression of kiwifruit (Actinidia chinensis) GOLDEN2-LIKE homolog elevates chloroplast level and nutritional quality in tomato (Solanum lycopersicum).

Constitutive expression of AchGLK from A. chinensis in transgenic tomato (S. lycopersicum) confers fruits an elevated plastid biogenesis with intensified granule thylakoid stacks and increased content of nutritional compounds. Plastid development is regulated by multiple environmental and genetic factors. Golden2-like (GLK) genes, members from GARP subfamily of the MYB transcription factors, have been shown to regulate plastid biogenesis and development in several species. In tomato (S. lycopersicum), SlGLK2 gene is expressed in the fruit in a manner of latitudinal gradient and determines the green shoulder phenotype. Here, we report the isolation and characterization of a kiwifruit (A. chinensis) GLK homolog (AchGLK). Transcription analysis showed that AchGLK is highly expressed in mature leaves and in fruits 60-day post-anthesis. Overexpression of AchGLK in transgenic tomato resulted in dark green immature fruit with higher concentration of chlorophyll and overall increased chloroplast compartment, both number and size. The ripened fruit had higher levels of carotenoids and sugars as well. Nevertheless, no phenotypic changes were observed in the transgenic leaves, similar to the previously described overexpression of SlGLK2 in tomato. Our study suggests that AchGLK is functionally homologous to tomato GLK2 with a potential in regulating plastid level in fruit that could contribute to improvement of fruit quality.

ShCIGT, a Trihelix family gene, mediates cold and drought tolerance by interacting with SnRK1 in tomato

Abiotic stress, such as drought and cold stress, have a major impact on plant growth and development. The trihelix transcription factor family plays important roles in plant morphological development and adaptation to abiotic stresses. In this study, we isolated a cold-induced gene named ShCIGT from the wild tomato species Solanum habrochaites and found that it contributes to abiotic stress tolerance. ShCIGT belongs to the GT-1 subfamily of the trihelix transcription factors. It was constitutively expressed in various tissues. Its expression was induced by multiple abiotic stresses and abscisic acid (ABA). Overexpression of ShCIGT in cultivated tomato enhanced cold and drought stress tolerance. In addition, the transgenic plants displayed a reduced sensitivity to ABA during post-germination growth. We found that ShCIGT interacts with SnRK1, an energy sensor in the metabolic signaling network, which controls plant metabolism, growth and development, and stress tolerance. Based on these data, we conclude ShCIGT may improve abiotic-stress tolerance in tomato by interacting with SnRK1.