Eukaryotic Transcription Factors Research Articles

Genome-Wide Identification and Expression Analysis of bHLH-MYC Family Genes from Mustard That May Be Important in Trichome Formation.

The trichomes of mustard leaves have significance due to their ability to combat unfavorable external conditions and enhance disease resistance. It was demonstrated that the MYB-bHLH-WD40 (MBW) ternary complex consists of MYB, basic Helix-Loop-Helix (bHLH), and WD40-repeat (WD40) family proteins and plays a key role in regulating trichome formation and density. The bHLH gene family, particularly the Myelocytomatosis (MYC) proteins that possess the structural bHLH domain (termed bHLH-MYC), are crucial to the formation and development of leaf trichomes in plants. bHLH constitutes one of the largest families of transcription factors in eukaryotes, of which MYC is a subfamily member. However, studies on bHLH-MYC transcription factors in mustard have yet to be reported. In this study, a total of 45 bHLH-MYC transcription factors were identified within the Brassica juncea genome, and a comprehensive series of bioinformatic analyses were conducted on their structures and properties: an examination of protein physicochemical properties, an exploration of conserved structural domains, an assessment of chromosomal positional distributions, an analysis of the conserved motifs, an evaluation of the gene structures, microsynteny analyses, three-dimensional structure prediction, and an analysis of sequence signatures. Finally, transcriptome analyses and a subcellular localization examination were performed. The results revealed that these transcription factors were unevenly distributed across 18 chromosomes, showing relatively consistent conserved motifs and gene structures and high homology. The final results of the transcriptome analysis and gene annotation showed a high degree of variability in the expression of bHLH-MYC transcription factors. Five genes that may be associated with trichome development (BjuVA09G22490, BjuVA09G13750, BjuVB04G14560, BjuVA05G24810, and BjuVA06G44820) were identified. The subcellular localization results indicated that the transcription and translation products of these five genes were expressed in the same organelle: the nucleus. This finding provides a basis for elucidating the roles of bHLH-MYC family members in plant growth and development, and the molecular mechanisms underlying trichome development in mustard leaves.

Rice transcription factor bHLH25 confers resistance to multiple diseases by sensing H2O2.

Hydrogen peroxide (H2O2) is a ubiquitous signal regulating many biological processes, including innate immunity, in all eukaryotes. However, it remains largely unknown that how transcription factors directly sense H2O2 in eukaryotes. Here, we report that rice basic/helix-loop-helix transcription factor bHLH25 directly senses H2O2 to confer resistance to multiple diseases caused by fungi or bacteria. Upon pathogen attack, rice plants increase the production of H2O2, which directly oxidizes bHLH25 at methionine 256 in the nucleus. Oxidized bHLH25 represses miR397b expression to activate lignin biosynthesis for plant cell wall reinforcement, preventing pathogens from penetrating plant cells. Lignin biosynthesis consumes H2O2 causing accumulation of non-oxidized bHLH25. Non-oxidized bHLH25 switches to promote the expression of Copalyl Diphosphate Synthase 2 (CPS2), which increases phytoalexin biosynthesis to inhibit expansion of pathogens that escape into plants. This oxidization/non-oxidation status change of bHLH25 allows plants to maintain H2O2, lignin and phytoalexin at optimized levels to effectively fight against pathogens and prevents these three molecules from over-accumulation that harms plants. Thus, our discovery reveals a novel mechanism by which a single protein promotes two independent defense pathways against pathogens. Importantly, the bHLH25 orthologues from available plant genomes all contain a conserved M256-like methionine suggesting the broad existence of this mechanism in the plant kingdom. Moreover, this Met-oxidation mechanism may also be employed by other eukaryotic transcription factors to sense H2O2 to change functions.

Divergence in a Eukaryotic Transcription Factor's co-TF Dependence Involves Multiple Intrinsically Disordered Regions Affecting Activation and Autoinhibition.

Combinatorial control by multiple transcription factors (TFs) is a hallmark of eukaryotic gene regulation. Despite its prevalence and crucial roles in enhancing specificity and integrating information, the mechanisms behind why eukaryotic TFs depend on one another, and whether such interdependence evolves, are not well understood. We exploit natural variation in co-TF dependence in the yeast phosphate starvation (PHO) response to address this question. In the model yeast Saccharomyces cerevisiae , the main TF, Pho4, relies on the co-TF Pho2 to regulate ∼28 genes. In a related yeast pathogen, Candida glabrata , its Pho4 exhibits significantly reduced Pho2 dependence and has an expanded target set of ∼70 genes. Biochemical analyses showed C. glabrata Pho4 (CgPho4) binds to the same consensus motif with 3-4-fold higher affinity than ScPho4 does. A machine-learning-based prediction and yeast one-hybrid assay identified two Intrinsically Disordered Regions (IDRs) in CgPho4 that boost the activity of the main activation domain but showed little to no activity on their own. We also found evidence for autoinhibition behind the co-TF dependence in ScPho4. An IDR in ScPho4 next to its DNA binding domain was found to act as a double-edged sword: it both allows for enhanced activity with Pho2, and inhibits Pho4's activity without Pho2. This study provides a detailed molecular picture of how co-TF dependence is mediated and how its evolution, mainly driven by IDR divergence, can lead to significant rewiring of the regulatory network.

Comprehensive Annotation and Expression Profiling of C2H2 Zinc Finger Transcription Factors across Chicken Tissues.

As the most abundant class of transcription factors in eukaryotes, C2H2-type zinc finger proteins (C2H2-ZFPs) play critical roles in various biological processes. Despite being extensively studied in mammals, C2H2-ZFPs remain poorly characterized in birds. Recent accumulation of multi-omics data for chicken enables the genome-wide investigation of C2H2-ZFPs in birds. The purpose of this study is to reveal the genomic occurrence and evolutionary signature of chicken C2H2-ZFPs, and further depict their expression profiles across diverse chicken tissues. Here, we annotated 301 C2H2-ZFPs in chicken genome, which are associated with different effector domains, including KRAB, BTB, HOMEO, PHD, SCAN, and SET. Among them, most KRAB-ZFPs lack orthologues in mammals and tend to form clusters by duplication, supporting their fast evolution in chicken. We also annotated a unique and previously unidentified SCAN-ZFP, which is lineage-specific and highly expressed in ovary and testis. By integrating 101 RNA-seq datasets for 32 tissues, we found that most C2H2-ZFPs have tissue-specific expression. Particularly, 74 C2H2-ZFPs-including 27 KRAB-ZFPs-show blastoderm-enriched expression, indicating their association with early embryo development. Overall, this study performs comprehensive annotation and expression profiling of C2H2 ZFPs in diverse chicken tissues, which gives new insights into the evolution and potential function of C2H2-ZFPs in avian species.

Genome-Wide Identification and Expression Analysis of the Cys2His2 Zinc Finger Protein Gene Family in Flammulina filiformis.

Zinc finger proteins (ZFPs) are essential transcription factors in eukaryotes, particularly the extensively studied C2H2 family, which is known for its involvement in various biological processes. This research provides a thorough examination and analysis of the C2H2-ZFP gene family in Flammulina filiformis. Using bioinformatics tools, 58 FfC2H2-ZFP genes spread across 11 chromosomes were identified and scrutinized in detail for their gene structures, protein characteristics, and phylogenetic relationships. The study of phylogenetics and synteny sheds light on the evolutionary relationships among C2H2-ZFPs in F. filiformis and other fungi, revealing a complex evolutionary past. The identification of conserved cis-regulatory elements in the gene promoter regions suggests intricate functionalities, particularly in the developmental and stress response pathways. By utilizing RNA-seq and qRT-PCR techniques, the expression patterns of these genes were explored across different developmental stages and tissues of F. filiformis, unveiling distinct expression profiles. Notably, significant expression variations were observed in the stipe elongation region and pilei of various sizes, indicating potential roles in fruiting body morphogenesis. This study enhances our knowledge of the C2H2-ZFP gene family in F. filiformis and lays the groundwork for future investigations into their regulatory mechanisms and applications in fungal biology and biotechnology.

Dynamic BTB-domain filaments promote clustering of ZBTB proteins

The formation of dynamic protein filaments contributes to various biological functions by clustering individual molecules together and enhancing their binding to ligands. We report such a propensity for the BTB domains of certain proteins from the ZBTB family, a large eukaryotic transcription factor family implicated in differentiation and cancer. Working with Xenopus laevis and human proteins, we solved the crystal structures of filaments formed by dimers of the BTB domains of ZBTB8A and ZBTB18 and demonstrated concentration-dependent higher-order assemblies of these dimers in solution. In cells, the BTB-domain filamentation supports clustering of full-length human ZBTB8A and ZBTB18 into dynamic nuclear foci and contributes to the ZBTB18-mediated repression of a reporter gene. The BTB domains of up to 21 human ZBTB family members and two related proteins, NACC1 and NACC2, are predicted to behave in a similar manner. Our results suggest that filamentation is a more common feature of transcription factors than is currently appreciated.

MTF1 genetic variants are associated with lung cancer risk in the Chinese Han population

BackgroundMetal-regulatory transcription factor 1 (MTF1), a conserved metal-binding transcription factor in eukaryotes, regulates the proliferation of cancer cells by activating downstream target genes and then participates in the formation and progression of tumors, including lung cancer (LC). The expression level of MTF1 is down-regulated in LC, and high expression of MTF1 is associated with a good prognosis of LC. However, the association between MTF1 polymorphism and LC risk has not been explored.MethodsThe genotyping of MTF1 Single nucleotide polymorphisms (SNPs) including rs473279, rs28411034, rs28411352, and rs3748682 was identified by the Agena MassARRAY system among 670 healthy controls and 670 patients with LC. The odds ratio (OR) and 95% confidence intervals (CI) were calculated by logistics regression to assess the association of these SNPs with LC risk.ResultsMTF1 rs28411034 (OR 1.22, 95% CI 1.03–1.45, p = 0.024) and rs3748682 (OR 1.24, 95% CI 1.04–1.47, p = 0.014) were associated with higher LC susceptibility overall. Moreover, the effect of rs28411034 and rs3748682 on LC susceptibility was observed in males, subjects with body mass index (BMI) ≥ 24 kg/m2, smokers, drinkers, and patients with lung squamous carcinoma (OR and 95% CI > 1, p < 0.05). Besides, rs28411352 (OR 0.73, 95% CI 0.55–0.97, p = 0.028,) showed protective effect for reduced LC risk in drinkers.ConclusionsWe were first who reported that rs28411034 and rs3748682 tended to be relevant to increased LC susceptibility among the Chinese Han population. These results of this study could help to recognize the pathogenic mechanisms of the MTF1 gene in LC progress.

C2H2 proteins: Evolutionary aspects of domain architecture and diversification.

The largest group of transcription factors in higher eukaryotes are C2H2 proteins, which contain C2H2-type zinc finger domains that specifically bind to DNA. Few well-studied C2H2 proteins, however, demonstrate their key role in the control of gene expression and chromosome architecture. Here we review the features of the domain architecture of C2H2 proteins and the likely origin of C2H2 zinc fingers. A comprehensive investigation of proteomes for the presence of proteins with multiple clustered C2H2 domains has revealed a key difference between groups of organisms. Unlike plants, transcription factors in metazoans contain clusters of C2H2 domains typically separated by a linker with the TGEKP consensus sequence. The average size of C2H2 clusters varies substantially, even between genomes of higher metazoans, and with a tendency to increase in combination with SCAN, and especially KRAB domains, reflecting the increasing complexity of gene regulatory networks.

GAGA zinc finger transcription factor searches chromatin by 1D-3D facilitated diffusion.

To elucidate how eukaryotic sequence-specific transcription factors (TFs) search for gene targets on chromatin, we used multi-color smFRET and single-particle imaging to track the diffusion of purified GAGA-Associated Factor (GAF) on DNA and nucleosomes. Monomeric GAF DNA-binding domain (DBD) bearing one zinc finger finds its cognate site by 1D or 3D diffusion on bare DNA and rapidly slides back-and-forth between naturally clustered motifs for seconds before escape. Multimeric, full-length GAF also finds clustered motifs on DNA by 1D-3D diffusion, but remains locked on target for longer periods. Nucleosome architecture effectively blocks GAF-DBD 1D-sliding into the histone core but favors retention of GAF-DBD when targeting solvent-exposed sites by 3D-diffusion. Despite the occlusive power of nucleosomes, 1D-3D facilitated diffusion enables GAF to effectively search for clustered cognate motifs in chromatin, providing a mechanism for navigation to nucleosome and nucleosome-free sites by a member of the largest TF family.

Comparative cofactor screens show the influence of transactivation domains and core promoters on the mechanisms of transcription.

Eukaryotic transcription factors (TFs) activate gene expression by recruiting cofactors to promoters. However, the relationships between TFs, promoters and their associated cofactors remain poorly understood. Here we combine GAL4-transactivation assays with comparative CRISPR-Cas9 screens to identify the cofactors used by nine different TFs and core promoters in human cells. Using this dataset, we associate TFs with cofactors, classify cofactors as ubiquitous or specific and discover transcriptional co-dependencies. Through a reductionistic, comparative approach, we demonstrate that TFs do not display discrete mechanisms of activation. Instead, each TF depends on a unique combination of cofactors, which influences distinct steps in transcription. By contrast, the influence of core promoters appears relatively discrete. Different promoter classes are constrained by either initiation or pause-release, which influences their dynamic range and compatibility with cofactors. Overall, our comparative cofactor screens characterize the interplay between TFs, cofactors and core promoters, identifying general principles by which they influence transcription.

DNA binding analysis of rare variants in homeodomains reveals homeodomain specificity-determining residues.

Homeodomains (HDs) are the second largest class of DNA binding domains (DBDs) among eukaryotic sequence-specific transcription factors (TFs) and are the TF structural class with the largest number of disease-associated mutations in the Human Gene Mutation Database (HGMD). Despite numerous structural studies and large-scale analyses of HD DNA binding specificity, HD-DNA recognition is still not fully understood. Here, we analyze 92 human HD mutants, including disease-associated variants and variants of uncertain significance (VUS), for their effects on DNA binding activity. Many of the variants alter DNA binding affinity and/or specificity. Detailed biochemical analysis and structural modeling identifies 14 previously unknown specificity-determining positions, 5 of which do not contact DNA. The same missense substitution at analogous positions within different HDs often exhibits different effects on DNA binding activity. Variant effect prediction tools perform moderately well in distinguishing variants with altered DNA binding affinity, but poorly in identifying those with altered binding specificity. Our results highlight the need for biochemical assays of TF coding variants and prioritize dozens of variants for further investigations into their pathogenicity and the development of clinical diagnostics and precision therapies.

Growth hormone resistance induced by amino acid deprivation in fao cells is independent of FGF21

Adequate dietary intake of amino acids is imperative for normal animal growth. Our previous work using rat hepatocarcinoma Fao cells demonstrated that growth hormone (GH) resistance, coupled with a concurrent reduction in insulin-like growth factor 1 (Igf1) mRNA levels, may underlie the growth retardation associated with a low-protein diet (LPD). In this study, we investigated whether FGF21 contributes to liver GH resistance in Fao rat hepatoma cells under amino acid deprivation conditions. Mice subjected to an LPD exhibited growth retardation, compromised GH signaling in the liver, and decreased blood IGF-1 levels compared with those on a control diet. To assess the potential involvement of fibroblast growth factor (FGF) 21, produced in response to amino acid deficiency, in the development of GH resistance, we examined GH signaling and Igf1 mRNA levels in Fao cells cultured in amino acid-deprived medium. Despite the inhibition of Fgf21 expression by the integrated stress response inhibitor, an inhibitor of the eukaryotic initiation factor 2-activating transcription factor 4 pathway, GH resistance persisted in response to amino acid deprivation. Additionally, the introduction of FGF21 into the control medium did not impair either GH signaling or GH-induced Igf1 transcription. These data suggest that, in Fao cells, amino acid deprivation induces GH resistance independently of FGF21 activity. By shedding light on the mechanisms behind growth retardation-associated GH resistance linked to amino acid deficiencies, our findings provide valuable insights for clinicians in formulating effective treatment strategies for individuals facing these challenges.

Structural and dynamical aspect of DNA motif sequence specific binding of AP-1 transcription factor.

Activator protein-1 (AP-1) comprises one of the largest and most evolutionary conserved families of ubiquitous eukaryotic transcription factors that act as a pioneer factor. Diversity in DNA binding interaction of AP-1 through a conserved basic-zipper (bZIP) domain directs in-depth understanding of how AP-1 achieves its DNA binding selectivity and consequently gene regulation specificity. Here, we address the structural and dynamical aspects of the DNA target recognition process of AP-1 using microsecond-long atomistic simulations based on the structure of the human AP-1 FosB/JunD bZIP-DNA complex. Our results show the unique role of DNA shape features in selective base specific interactions, characteristic ion population, and solvation properties of DNA grooves to form the motif sequence specific AP-1-DNA complex. The TpG step at the two terminals of the AP-1 site plays an important role in the structural adjustment of DNA by modifying the helical twist in the AP-1 bound state. We addressed the role of intrinsic motion of the bZIP domain in terms of opening and closing gripper motions of DNA binding helices, in target site recognition and binding of AP-1 factors. Our observations suggest that binding to the cognate motif in DNA is mainly accompanied with the precise adjustment of closing gripper motion of DNA binding helices of the bZIP domain.

Intrinsic protein disorder is insufficient to drive subnuclear clustering in embryonic transcription factors.

Modern microscopy has revealed that core nuclear functions, including transcription, replication, and heterochromatin formation, occur in spatially restricted clusters. Previous work from our lab has shown that subnuclear high-concentration clusters of transcription factors may play a role in regulating RNA synthesis in the early Drosophila embryo. A nearly ubiquitous feature of eukaryotic transcription factors is that they contain intrinsically disordered regions (IDRs) that often arise from low complexity amino acid sequences within the protein. It has been proposed that IDRs within transcription factors drive co-localization of transcriptional machinery and target genes into high-concentration clusters within nuclei. Here, we test that hypothesis directly, by conducting a broad survey of the subnuclear localization of IDRs derived from transcription factors. Using a novel algorithm to identify IDRs in the Drosophila proteome, we generated a library of IDRs from transcription factors expressed in the early Drosophila embryo. We used this library to perform a high-throughput imaging screen in Drosophila Schneider-2 (S2) cells. We found that while subnuclear clustering does not occur when the majority of IDRs are expressed alone, it is frequently seen in full-length transcription factors. These results are consistent in live Drosophila embryos, suggesting that IDRs are insufficient to drive the subnuclear clustering behavior of transcription factors. Furthermore, the clustering of transcription factors in living embryos was unaffected by the deletion of IDR sequences. Our results demonstrate that IDRs are unlikely to be the primary molecular drivers of the clustering observed during transcription, suggesting a more complex and nuanced role for these disordered protein sequences.

Intrinsic protein disorder is insufficient to drive subnuclear clustering in embryonic transcription factors

Modern microscopy has revealed that core nuclear functions, including transcription, replication, and heterochromatin formation, occur in spatially restricted clusters. Previous work from our lab has shown that subnuclear high-concentration clusters of transcription factors may play a role in regulating RNA synthesis in the early Drosophila embryo. A nearly ubiquitous feature of eukaryotic transcription factors is that they contain intrinsically disordered regions (IDRs) that often arise from low complexity amino acid sequences within the protein. It has been proposed that IDRs within transcription factors drive co-localization of transcriptional machinery and target genes into high-concentration clusters within nuclei. Here, we test that hypothesis directly, by conducting a broad survey of the subnuclear localization of IDRs derived from transcription factors. Using a novel algorithm to identify IDRs in the Drosophila proteome, we generated a library of IDRs from transcription factors expressed in the early Drosophila embryo. We used this library to perform a high-throughput imaging screen in Drosophila Schneider-2 (S2) cells. We found that while subnuclear clustering does not occur when the majority of IDRs are expressed alone, it is frequently seen in full-length transcription factors. These results are consistent in live Drosophila embryos, suggesting that IDRs are insufficient to drive the subnuclear clustering behavior of transcription factors. Furthermore, the clustering of transcription factors in living embryos was unaffected by the deletion of IDR sequences. Our results demonstrate that IDRs are unlikely to be the primary molecular drivers of the clustering observed during transcription, suggesting a more complex and nuanced role for these disordered protein sequences.

Genetic variants and mRNA expression of KLF4 and KLF5 with hypertension: A combination of case-control study and cohort study.

Hypertension (HT) is a major risk factor for cardiovascular diseases. Krüppel-like factors (KLFs) are important transcription factors in eukaryotes. Studies have reported that KLF4 and KLF5 are correlated with several cardiovascular diseases, whereas population studies for associations between HT and KLF4 or KLF5 have been rarely reported. Thus, the current study aimed to examines the association of genetic variants and mRNA expression levels of KLF4 and KLF5 with HT, as well as the effect of antihypertensive drugs on the expression levels. The associations of one single-nucleotide polymorphism (SNP) in KLF4 and three SNPs in KLF5 with HT were investigated using a combination of case-control and cohort studies. The study population were selected from a community-based population cohort in four different regions of Jiangsu Province. Risks of HT were estimated through logistic and Cox regression analyses, respectively. In addition, mRNA expression levels of KLF4 and KLF5 were measured in 246 controls and 385 HT cases selected from the cohort study as mentioned above. Among the HT cases, 263 were not taking antihypertensive drugs [AHD(-)] and 122 were taking antihypertensive drugs [AHD(+)]. In the case-control study, SNP rs9573096 (C>T) in KLF5 was significantly associated with an increased risk of HT in the additive model (adjusted odds ratio [OR], 1.106; 95% confidence interval [CI], 1.009 to 1.212). In the cohort study of the normotensive population, rs9573096 in KLF5 was also significantly associated with an increased risk of HT in the additive model (adjusted hazards ratio [HR], 1.199; 95% CI, 1.070 to 1.344). KLF4 and KLF5 mRNA expression levels were significantly higher in the AHD(-) group than in the control group ( P < 0.05), but lower in the AHD(+) group than in the AHD(-) group ( P < 0.05). The current study demonstrated the associations of KLF4 and KLF5 genetic variants with hypertension, and the indicative discriminations of mRNA expression levels of KLF4 and KLF5 for risk of hypertension and antihypertensive treatment.

Protein-Protein Interaction via Two-Hybrid Assay in Yeast.

The yeast two-hybrid assay enables detecting interactions between proteins, which makes this tool of particular interest for plant-virus interaction studies. Basically, the reporter gene expression (HIS3) is activated by the binding of a transcription factor GAL4, which, like eukaryotic transcription factors, is modular in nature and consists of two structurally independent domains: DNA-binding (DB) and activation (AD) domains. The two proteins under investigation are expressed separately, one fused to the BD domain and the other to the AD domain. In the yeast strain AH109, activation of the reporter gene occurs only in cells that contain interacting proteins, reconstituting the transcription factor GAL4 which then binds to the responsive promoter and results in yeast colony growth.

Sesquiterpene Lactones as Potential G1/S Phase Cell Cycle Inhibitors: A Molecular Docking Study

Cell cycle checkpoints play a crucial role in cell division by monitoring the orderly progression of each phase, ensuring accurate completion before advancing to the next stage. They act as quality control mechanisms, pausing the cell cycle when optimal conditions are not met, thereby preventing errors during cell division. Objective: To discover Sesquiterpene Lactones (SLs) as inhibitory compounds targeting Cyclin D1/Cyclin Dependent Kinase 4 (CDK4)- Cyclin Dependent kinase 6 (CDK6) complex and Eukaryotic Transcription Factor 2 protein (E2F-2). Methods: The inhibitory potential of SLs, namely ilicol, eucalyptone, and ascleposide E, was investigated using molecular docking analysis. The docking and visualization of ligand-protein complexes were performed using MGL Tools version 1.5.7, BIOVIA Discovery Studio version 21.1.0, and PyMol version 2.5.2. Additionally, drug likeness and pharmacokinetic properties of SLs were assessed via pkCSM and ADMET analysis. Results: Findings demonstrate that ilicol exhibit most favourable complex with CDK6 having binding energy of –7.8 kCal/mol and inhibition constant 1.81 μM. The visualization of ligand-receptor complexes reveals substantial hydrogen bonding interactions. Conclusions: Current study revealed that novel SLs show favourable drug likeness and promising ADMET profile along with strong inhibitory effect on G1/S regulatory proteins. The potency of SLs is in order of ilicol&gt; ascleposide E&gt;eucalyptone. To further validate the inhibitory effect of ilicol, implementation of comprehensive in vitro and in vivo investigations must be employed for progression of its development as a novel anti-cancer therapeutic.

Dimerization choice and alternative functions of ZBTB transcription factors.

Zinc Finger DNA-binding domain-containing proteins are the most populous family among eukaryotic transcription factors. Among these, members of the BTB domain-containing ZBTB sub-family are mostly known for their transcriptional repressive functions. In this Viewpoint article, we explore molecular mechanisms that potentially diversify the function of ZBTB proteins based on their homo and heterodimerization, alternative splicing and post-translational modifications. We describe how the BTB domain is as much a scaffold for the assembly of co-repressors, as a domain that regulates protein stability. We highlight another mechanism that regulates ZBTB protein stability: phosphorylation in the zinc finger domain. We explore the non-transcriptional, structural roles of ZBTB proteins and highlight novel findings that describe the ability of ZBTB proteins to associate with poly adenosine ribose in the nucleus during the DNA damage response. Herein, we discuss the contribution of BTB domain scaffolds to the formation of transcriptional repressive complexes, to chromosome compartmentalization and their non-transcriptional, purely structural functions in the nucleus.

Genome-Wide Identification, Classification and Expression Analyses of MADS-Box Genes Reveal Their Role in Stem Gall Formation and Expansion of Zizania latifolia

MADS-box genes are important transcription factors in eukaryotes that are involved in regulating the growth and development of many plants. Jiaobai is a special aquatic vegetable formed through the stem expansion of Zizania latifolia infected by Ustilago esculenta and is wildly cultivated in Southeast Asia. To date, the biological function of MADS-box genes in Z. latifolia remains largely unknown. In this study, a genome-wide search for MADS-box genes in Z. latifolia was performed, and 87 MADS-box genes were identified. According to the phylogenetic analysis, there were 27 type I genes and 60 type II genes. The type I genes were mainly distributed in the Mα, Mβ and Mγ subfamilies, and the type II genes were divided into 14 subfamilies and unevenly distributed across 17 chromosomes. The encoded protein sequences ranged from 91 to 433 amino acids, the number of exons was 1~14, and most type I genes did not contain introns. The promoter region contained a large number of functional domains related to light response, plant hormones, stress and the meristem. An analysis of the expression patterns showed that there were massive differences in the expression of the MADS-box genes in different tissues, with six genes highly expressed in leaves and eight genes highly expressed in the stem apical meristem. Photoperiod and temperature were found to regulate the formation of the stem gall (SG) of Z. latifolia, and short-day (SD) conditions had an obvious promoting effect. ZlMADS57 and ZlMADS85 were significantly increased in SG under SD. Further analysis of the expression levels of MADS-box genes during the developmental stages of Z. latifolia found that the ZlMADS45, ZlMADS57, ZlMADS81 and ZlMADS85 were highly expressed 10 days before the SG formation, and ZlMADS66 reached its highest value on the day when the SG began forming. ZlMADS14, ZlMADS15, ZlMADS32, ZlMADS36, ZlMADS59 and ZlMADS71 were highly expressed after SG expansion, indicating that the MADS-box gene may play an important role in regulating SG formation and the subsequent expansion of Jiaobai. This study provides a reference for the functional identification of the MADS-box gene family and establishes a foundation for regulating the maturity of Z. latifolia.