Carboxyl-terminal Region Research Articles

Identification of ASYNAPTIC4, a Component of the Meiotic Chromosome Axis.

During the leptotene stage of prophase I of meiosis, chromatids become organized into a linear looped array via a protein axis that forms along the loop bases. Establishment of the axis is essential for the subsequent synapsis of the homologous chromosome pairs and the progression of recombination to form genetic crossovers. Here, we describe ASYNAPTIC4 (ASY4), a meiotic axis protein in Arabidopsis (Arabidopsis thaliana). ASY4 is a small coiled-coil protein that exhibits limited sequence similarity with the carboxyl-terminal region of the axis protein ASY3. We used enhanced yellow fluorescent protein-tagged ASY4 to show that ASY4 localizes to the chromosome axis throughout prophase I. Bimolecular fluorescence complementation revealed that ASY4 interacts with ASY1 and ASY3, and yeast two-hybrid analysis confirmed a direct interaction between ASY4 and ASY3. Mutants lacking full-length ASY4 exhibited defective axis formation and were unable to complete synapsis. Although the initiation of recombination appeared to be unaffected in the asy4 mutant, the number of crossovers was reduced significantly, and crossovers tended to group in the distal parts of the chromosomes. We conclude that ASY4 is required for normal axis and crossover formation. Furthermore, our data suggest that ASY3/ASY4 are the functional homologs of the mammalian SYCP2/SYCP3 axial components.

Syntrophin binds directly to multiple spectrin-like repeats in dystrophin and mediates binding of nNOS to repeats 16-17.

Mutation of the gene encoding dystrophin leads to Duchenne and Becker muscular dystrophy (DMD and BMD). Currently, dystrophin is thought to function primarily as a structural protein, connecting the muscle cell actin cytoskeleton to the extra-cellular matrix. In addition to this structural role, dystrophin also plays an important role as a scaffold that organizes an array of signaling proteins including sodium, potassium, and calcium channels, kinases, and nitric oxide synthase (nNOS). Many of these signaling proteins are linked to dystrophin via syntrophin, an adapter protein that is known to bind directly to two sites in the carboxyl terminal region of dystrophin. A search of the dystrophin sequence revealed three additional potential syntrophin binding sites (SBSs) within the spectrin-like repeat (SLR) region of dystrophin. Binding assays revealed that the site at SLR 17 bound specifically to the α isoform of syntrophin while the site at SLR 22 bound specifically to the β-syntrophins. The SLR 17 α-SBS contained the core sequence known to be required for nNOS-dystrophin interaction. In vitro and in vivo assays indicate that α-syntrophin facilitates the nNOS-dystrophin interaction at this site rather than nNOS binding directly to dystrophin as previously reported. The identification of multiple SBSs within the SLR region of dystrophin demonstrates that this region functions as a signaling scaffold. The signaling role of the SLR region of dystrophin will need to be considered for effective gene replacement or exon skipping based DMD/BMD therapies.

Molecular mechanism of ER stress-induced pre-emptive quality control involving association of the translocon, Derlin-1, and HRD1

The maintenance of endoplasmic reticulum (ER) homeostasis is essential for cell function. ER stress-induced pre-emptive quality control (ERpQC) helps alleviate the burden to a stressed ER by limiting further protein loading. We have previously reported the mechanisms of ERpQC, which includes a rerouting step and a degradation step. Under ER stress conditions, Derlin family proteins (Derlins), which are components of ER-associated degradation, reroute specific ER-targeting proteins to the cytosol. Newly synthesized rerouted polypeptides are degraded via the cytosolic chaperone Bag6 and the AAA-ATPase p97 in the ubiquitin-proteasome system. However, the mechanisms by which ER-targeting proteins are rerouted from the ER translocation pathway to the cytosolic degradation pathway and how the E3 ligase ubiquitinates ERpQC substrates remain unclear. Here, we show that ERpQC substrates are captured by the carboxyl-terminus region of Derlin-1 and ubiquitinated by the HRD1 E3 ubiquitin ligase prior to degradation. Moreover, HRD1 forms a large ERpQC-related complex composed of Sec61α and Derlin-1 during ER stress. These findings indicate that the association of the degradation factor HRD1 with the translocon and the rerouting factor Derlin-1 may be necessary for the smooth and effective clearance of ERpQC substrates.

Protein E6 in High Risk Human Papillomaviruses

Human Papillomavirus (HPV) refers to a group of more than one hundred HPV high risk or low risk strains associated with a variety of conditions. Over fifty strains lead to genital infections, while others influence the development of various cancers, such as cervical, skin, etc. The combination of HPV E6/E7, hTERT, and Ki67 mRNA expression levels complement each other to diagnose lesions of the aforementioned cancers, specifically dealing with the cervix. All HPV strains share a common structure: circular, double stranded DNA encoding for eight open reading frames (ORF) surrounded by a non‐enveloped capsid. ORFs function to produce the E1‐E7 proteins needed for HPV replication (early region), L1‐L2 proteins that make up the capsid (late region), and replicate and transcribe viral DNA with the help of cis components (long control region). The E6, in particular, is an oncoprotein composed of polypeptides made up of 150 amino acids and a Cys‐X‐X‐Cys motif that allow for the formation of two zinc fingers. E6 and E7 recognize a number of host proteins by hijacking their cellular domain‐motif interaction networks. In the HPV‐16 and HPV‐18 strains, the E6 protein binds its amino and carboxyl terminal regions to a leucine‐rich sequence (LxxLL) within the cellular ubiquitin ligase, E6AP. This heterodimer degrades p53, a proapoptotic tumor suppressor, although the exact mode of assembly is unknown. Complete degradation potentially leads to oncogenesis in high‐risk HPV strains, as these transformed cells have lost their ability to arrest at the G1 checkpoint within their cell cycle and perform apoptosis. Aside from the E6‐E6AP heterodimer binding directly to p53, the E6 protein has other oncogenic functions, allowing it to bind to four general classes of other proteins, providing indirect pathways to degrade p53. Binding options include proteins involved in cell polarity and motility, tumor suppressors and inducers of apoptosis, transcriptional coactivators and DNA replication/repair factors. Regarding transcription coactivators, degradation of p53 transcriptional activity is possible, as seen by the targeting of p53 coactivator p300/CBP or yADA3. Given the mechanism of E6‐E6AP complex hindering p53's from carrying out normal function, E6 is an attractive target for therapies against cervical cancers. The Olathe North High School MSOE Center for BioMolecular Modeling SMART Team used 3‐D modeling and printing technology to examine structure‐function relationships of E6.Support or Funding InformationSMART team is a joint venture between the Milwaukee School of Engineering and the Olathe School District's 21st century program Medical Professions Academy.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Molecular characterization of two sub-family specific monoclonal antibodies to meningococcal Factor H binding protein

Factor H binding protein (FHbp) is a component of two licensed vaccines for prevention of sepsis and meningitis caused by serogroup B meningococci. FHbp binds human Factor H (FH), which contributes to evasion of host immunity and FHbp sequence variants can be classified into two sub-families. Antibodies against FHbp elicit complement-mediated killing and can inhibit recruitment of FH to the bacterial surface. We report epitope mapping studies of two murine IgG mAbs, designated JAR 31 and JAR 36, isolated from a mouse immunized with FHbp in sub-family A, which is present in ∼30–40% of invasive isolates. In the present study, we tested the reactivity of mAbs JAR 31 and JAR 36 with seven natural FHbp sequence variants from different phylogenic groups. We screened bacteriophage-displayed peptide libraries to identify amino acid residues contributing to the JAR 36 epitope. Based on the reactivities of mAbs JAR 31 and JAR 36 with the seven FHbp variants, and the frequent occurrences of aspartate (D) and lysine (K) residues in the JAR 36-bound phage peptides, we selected six residues in the carboxyl-terminal region of FHbp for replacement with alanine (A). The D201A and K203A substitutions respectively eliminated and decreased binding of mAbs JAR 31 and JAR 36 to FHbp. These substitutions did not affect binding of the control mAb JAR 33 or of human FH. JAR 31 or JAR 36 mediated cooperative complement-mediated bactericidal activity with other anti-FHbp mAbs. The identification of two amino acid residues involved in the epitopes recognized by these anti-FHbp mAbs may contribute to a more complete understanding of the spatial requirements for cooperative anti-FHbp mAb bactericidal activity.

ASK family kinases mediate cellular stress and redox signaling to circadian clock

Daily rhythms of behaviors and physiologies are generated by the circadian clock, which is composed of clock genes and the encoded proteins forming transcriptional/translational feedback loops (TTFLs). The circadian clock is a self-sustained oscillator and flexibly responds to various time cues to synchronize with environmental 24-h cycles. However, the key molecule that transmits cellular stress to the circadian clockwork is unknown. Here we identified apoptosis signal-regulating kinase (ASK), a member of the MAPKKK family, as an essential mediator determining the circadian period and phase of cultured cells in response to osmotic changes of the medium. The physiological impact of ASK signaling was demonstrated by a response of the clock to changes in intracellular redox states. Intriguingly, the TTFLs drive rhythmic expression of Ask genes, indicating ASK-mediated association of the TTFLs with intracellular redox. In behavioral analysis, Ask1, Ask2, and Ask3 triple-KO mice exhibited compromised light responses of the circadian period and phase in their activity rhythms. LC-MS/MS-based proteomic analysis identified a series of ASK-dependent and osmotic stress-responsive phosphorylations of proteins, among which CLOCK, a key component of the molecular clockwork, was phosphorylated at Thr843 or Ser845 in the carboxyl-terminal region. These findings reveal the ASK-dependent stress response as an underlying mechanism of circadian clock flexibility.

VPS28, an ESCRT-I protein, regulates mitotic spindle organization via Gβγ, EG5 and TPX2

The mitotic spindle is a dynamic macromolecular complex essential for chromosome segregation. ESCRT (endosomal sorting complexes required for transport) proteins are emerging as relevant mitotic players putatively recruiting spindle organizers. Here, we describe that VPS28, an ESCRT-I component, directly interacts with Gβγ, a signaling heterodimer with documented impact on microtubule dynamics, composing a novel organizer of the mitotic spindle aster. We found that VPS28 localizes to mitotic microtubules where it recruits Gβγ. Reducing VPS28 expression impairs kinesin Eg5 and TPX2 localization to the mitotic spindle. The interaction between VPS28 and Gβγ involves the carboxyl-terminal region of VPS28, which usually interacts with VPS36, its regular partner at multivesicular bodies. The VPS28-Gβγ complex is better constituted in the presence of Gα independently of G protein coupled receptor-stimulation, suggesting an intrinsic mechanism of regulation by which this novel complex contributes to mitotic spindle organization in mammalian cells.

Relationship between the dimerization of thyroglobulin and its ability to form triiodothyronine

Thyroglobulin (TG) is the most abundant thyroid gland protein, a dimeric iodoglycoprotein (660 kDa). TG serves as the protein precursor in the synthesis of thyroid hormones tetraiodothyronine (T4) and triiodothyronine (T3). The primary site for T3 synthesis in TG involves an iodotyrosine acceptor at the antepenultimate Tyr residue (at the extreme carboxyl terminus of the protein). The carboxyl-terminal region of TG comprises a cholinesterase-like (ChEL) domain followed by a short unique tail sequence. Despite many studies, the monoiodotyrosine donor residue needed for the coupling reaction to create T3 at this evolutionarily conserved site remains unidentified. In this report, we have utilized a novel, convenient immunoblotting assay to detect T3 formation after protein iodination in vitro, enabling the study of T3 formation in recombinant TG secreted from thyrocytes or heterologous cells. With this assay, we confirm the antepenultimate residue of TG as a major T3-forming site, but also demonstrate that the side chain of this residue intimately interacts with the same residue in the apposed monomer of the TG dimer. T3 formation in TG, or the isolated carboxyl-terminal region, is inhibited by mutation of this antepenultimate residue, but we describe the first substitution mutation that actually increases T3 hormonogenesis by engineering a novel cysteine, 10 residues upstream of the antepenultimate residue, allowing for covalent association of the unique tail sequences, and that helps to bring residues Tyr2744 from apposed monomers into closer proximity.

Enhancement of the thermostability of mouse claudin-3 on complex formation with the carboxyl-terminal region of Clostridium perfringens enterotoxin improves crystal quality.

Tight junctions regulate substance permeation through intercellular spaces as a physical barrier or a paracellular pathway, and play an important role in maintaining the internal environment. Claudins, which are tetraspan-transmembrane proteins, are pivotal components of tight junctions. In mammals 27 claudin subtypes have been identified, each of which interacts with specific subtypes. Although the crystal structures of several subtypes have been determined, the molecular mechanisms underlying subtype specificity remain unclear. Here, mouse claudin-3 (mCldn3) was crystallized in complex with the C-terminal region of Clostridium perfringens enterotoxin (C-CPE) for the structural analysis of an additional claudin subtype. mCldn3 alone was difficult to crystallize, but complex formation with C-CPE enhanced the thermostability of mCldn3 and facilitated its crystallization. The introduction of an S313A mutation into C-CPE further improved its thermostability, and the resolution limits of the diffraction data sets improved from 8 Å for the wild-type complex to 4.7 Å for the S313A mutant complex.

Truncated JFH1 E2 Protein: Is it Reliable to be Used in Diagnostic ELISA Test and as a Protein-Based Vaccine Candidate?

HCV E2 glycoprotein is one of the most attractive proteins for designing an effective vaccine. Deletion of hydrophobic carboxyl-terminal region of this protein is necessary for its secretion, especially when it is expressed in E-coli. In this study we expressed this protein in truncated form and evaluated its application in developing an ELISA test and induction of humoral response in immunized mice. The purpose of this study was expression of HCV truncated E2 protein from JFH1 strain in E-coli BL21(DE3) and evaluation of its antigenicity. Truncated E2 region from HCV genotype 2a (JFH1) was amplified by PCR and cloned into a pET28a (+) vector and was used to transform the E-coli DH5α strain. The recombinant E2 protein was evaluated both in an ELISA test and induction of humoral immunity in mice. Truncated E2 protein was expressed in BL21(DE3). Its specific antibody was detected in serum samples from HCV infected patients. Also, it could elicit a significant humoral immunity in mice. Truncated form of E2 protein which has been expressed in E-coli could be used as an effective antigen both in diagnostic tests such as ELISA and also, as a protein-based vaccine candidate.

Co-Expression of hbha and mtb32C Genes from Mycobacterium tuberculosis H37Rv in a Prokaryotic System

Background: Heparin-binding hemagglutinin (HBHA) protein is a surface adhesin that mediates the attachment of Mycobacterium tuberculosis to host cells by its own unique, carboxyl-terminal region. The methylated HBHA has a specific motif with a lysine-, alanine-, and proline-rich domain. More recently, it has been shown that HBHA protein has potential activity in stimulating immune responses, and is a promising new candidate for diagnostic applications besides a protective antigen against tuberculosis. Objectives: The aim of this study was to isolate a mycobacterial latency gene (hbha), and subsequently produce its protein as a new antigen for the Interferon-Gamma Release Assay test (IGRAs). Methods: In the present work, hbha and mtb32C genes were isolated from the Mycobacterium tuberculosis H37Rv genome using the polymerase chain reaction (PCR) method. The PCR products and pet21+ vector were digested with specific restriction enzymes and then submitted to the ligation procedure. Escherichia coli BL21-CodonPlus (DE3) competent cells were transformed with the recombinant mtb32C-hbha -pet21+ vector. Expression of recombinant protein (Mtb32C-HBHA) was confirmed with Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) and western blot methods. Results: Detection of a 500-bp gene and sequencing of recombinant pet-mtb32C-hbha vector, all confirmed the accuracy of the cloning procedure. A 36-KDa band of Mtb32C-HBHA protein was also detected by western blotting. Conclusions: In this study, expression of Mtb32C-HBHA protein was successfully done, in the prokaryotic system. Further studies are needed to evaluate the efficacy of recombinant Mtb32C-HBHA protein in diagnosis of latent tuberculosis.

Coiled-coil motif in LBD16 and LBD18 transcription factors are critical for dimerization and biological function in arabidopsis

ABSTRACTThe LATERAL ORGAN BOUNDARIES (LOB) DOMAIN (LBD) gene family members encode a class of plant-specific transcription factors that play important roles in many different aspects of plant growth and development. The LBD proteins contain a conserved LOB domain harboring a Leu zipper-like coiled-coil motif, which has been predicted to mediate protein-protein interactions among the LBD family members. Dimerization of transcription factors is crucial for the modulation of their DNA-binding affinity, specificity, and diversity, contributing to the transcriptional regulation of distinct cellular and biological responses. Our various molecular and biochemical experiments with genetic approaches on LBD16 and LBD18, which are known to control lateral root development in Arabidopsis, demonstrated that the conserved Leu or Val residues in the coiled-coil motifs of these transcription factors are critical for their dimerization as well as the transcriptional regulation to display their biological functions during lateral root formation. We further showed that beside the coiled-coil motif, the carboxyl-terminal region in LBD18 acts as an additional dimerization domain. These findings provide a molecular framework for the homo- and hetero-dimerization of the LBD family proteins for displaying their distinct and diverse biological functions in plants.

Production and characterization of polyclonal antibody against Arabidopsis GIGANTEA, a circadian clock controlled flowering time regulator

Arabidopsis GIGANTEA (GI) is encoded by a single gene and highly conserved among vascular plants and its mutants display pleiotropic phenotypes involved in diverse biological processes such as light signaling, circadian clock, and sucrose metabolism as well as abiotic stress responses. However, molecular mechanisms of GI are largely unknown due to the lack of useful antibody. To date, the epitope tags have been widely used to detect GI in plants, but it needs to generate the transgenic plants which take a few months. Here, we produced polyclonal α-GI antibody using truncated variants of GI having amino-terminal (1–858 aa) and carboxyl-terminal (920–1173) regions as antigens. Both recombinant His-GI1-858 and His-GI920–1173 proteins were individually and successfully expressed in E. coli and immunized into rabbit. Anti-serum was purified by antigenspecific affinity purification method using both recombinant His-GI1–858 and His-GI920–1173 proteins. Purified polyclonal α-GI antibody not only detected endogenous GI proteins in wild-type Arabidopsis plants, but also reenacted its diel oscillations. Furthermore, the antibody showed cross-reactivity with the GI orthologs in other plants such as Chinese cabbage, rape and tomato. Our polyclonal GI antibody could help to determine the molecular mechanisms of GI involved in largely unknown pleiotropic responses in plants.

Dissection of mammalian orthoreovirus µ2 reveals a self-associative domain required for binding to microtubules but not to factory matrix protein µNS.

Mammalian orthoreovirus protein μ2 is a component of the viral core particle. Its activities include RNA binding and hydrolysis of the γ-phosphate from NTPs and RNA 5´-termini, suggesting roles as a cofactor for the viral RNA-dependent RNA polymerase, λ3, first enzyme in 5´-capping of viral plus-strand RNAs, and/or prohibitory of RNA-5´-triphosphate-activated antiviral signaling. Within infected cells, μ2 also contributes to viral factories, cytoplasmic structures in which genome replication and particle assembly occur. By associating with both microtubules (MTs) and viral factory matrix protein μNS, μ2 can anchor the factories to MTs, the full effects of which remain unknown. In this study, a protease-hypersensitive region allowed μ2 to be dissected into two large fragments corresponding to residues 1–282 and 283–736. Fusions with enhanced green fluorescent protein revealed that these amino- and carboxyl-terminal regions of μ2 associate in cells with either MTs or μNS, respectively. More exhaustive deletion analysis defined μ2 residues 1–325 as the minimal contiguous region that associates with MTs in the absence of the self-associating tag. A region involved in μ2 self-association was mapped to residues 283–325, and self-association involving this region was essential for MT-association as well. Likewise, we mapped that μNS-binding site in μ2 relates to residues 290–453 which is independent of μ2 self-association. These findings suggest that μ2 monomers or oligomers can bind to MTs and μNS, but that self-association involving μ2 residues 283–325 is specifically relevant for MT-association during viral factories formation.

Protoplast Swelling and Hypocotyl Growth Depend on Different Auxin Signaling Pathways.

Members of the TRANSPORT INHIBITOR RESPONSE1/AUXIN SIGNALING F-BOX PROTEIN (TIR1/AFB) family are known auxin receptors. To analyze the possible receptor function of AUXIN BINDING PROTEIN1 (ABP1), an auxin receptor currently under debate, we performed different approaches. We performed a pharmacological approach using α-(2,4-dimethylphenylethyl-2-oxo)-indole-3-acetic acid (auxinole), α-(phenylethyl-2-oxo)-indole-3-acetic acid (PEO-IAA), and 5-fluoroindole-3-acetic acid (5-F-IAA) to discriminate between ABP1- and TIR1/AFB-mediated processes in Arabidopsis (Arabidopsis thaliana). We used a peptide of the carboxyl-terminal region of AtABP1 as a tool. We performed mutant analysis with the null alleles of ABP1, abp1-c1 and abp1-TD1, and the TILLING mutant abp1-5 We employed Coimbra, an accession that exhibits an amino acid exchange in the auxin-binding domain of ABP1. We measured either volume changes of single hypocotyl protoplasts or hypocotyl growth, both at high temporal resolution. 5-F-IAA selectively activated the TIR1/AFB pathway but did not induce protoplast swelling; instead, it showed auxin activity in the hypocotyl growth test. In contrast, PEO-IAA induced an auxin-like swelling response but no hypocotyl growth. The carboxyl-terminal peptide of AtABP1 induced an auxin-like swelling response. In the ABP1-related mutants and Coimbra, no auxin-induced protoplast swelling occurred. ABP1 seems to be involved in mediating rapid auxin-induced protoplast swelling, but it is not involved in the control of rapid auxin-induced growth.

In vitro and in vivo antimicrobial activity of a synthetic peptide derived from the C-terminal region of human chemokine CCL13 against Pseudomonas aeruginosa

Chemokines are important mediators of immunological responses during inflammation and under steady-state conditions. In addition to regulating cell migration, some chemotactic cytokines have direct effects on bacteria. Here, we characterized the antibacterial ability of the synthetic oligopeptide CCL1357-75, which corresponds to the carboxyl-terminal region of the human chemokine CCL13. In vitro measurements indicated that CCL1357-75 disrupts the cell membrane of Pseudomonas aeruginosa through a mechanism coupled to an unordered-helicoidal conformational transition. In a murine pneumonic model, CCL1357-75 improved mouse survival and bacterial clearance and decreased neutrophil recruitment, proinflammatory cytokines and lung pathology compared with that observed in untreated infected animals. Overall, our study supports the ability of chemokines and/or chemokine-derived oligopeptides to act as direct defense agents against pathogenic bacteria and suggests their potential use as alternative antibiotics.

Tyro3 carboxyl terminal region confers stability and contains the autophosphorylation sites

Tyro3, a member of TAM receptor tyrosine kinase family has been suggested to be autophosphorylated upon activation. In the current study we mapped the autophosphorylation sites of murine Tyro3 to tyrosine 723 and 756, with K540 being required for its kinase activity. Knockdown of Axl significantly decreases the tyrosyl-phosphorylation of Tyro3 in fibroblasts NR6WT, suggesting an interaction among the TAM family members. Interestingly, the carboxyl terminal region of Tyro3 is required for its stability in cells with a minimal length of 1–778 amino acids which is not conserved in murine Axl, a member of TAM. These data suggest that the autophosphorylation sites of TAM RTK members are unique although they share high similarity in amino acids within their carboxyl kinase domain.

Anti-androgenic mechanisms of Bisphenol A involve androgen receptor signaling pathway.

We have shown Bisphenol A (BPA) acts as an androgen receptor (AR) antagonist in the previous study. However, the mechanisms underlying anti-androgenic effects of BPA remain unclear. The objective of this study was to explore whether the AR signaling was involved in AR antagonism of BPA. The Cell Counting Kit-8 (CCK-8) assay and Real-Time Cell Analysis (RTCA) iCELLigence system were applied to analyze the mouse Sertoli cell TM4 proliferation. The mammalian two-hybrid assays were performed to investigate the effects of BPA on the AR amino- and carboxyl-terminal regions (N/C) interaction and the interactions of the AR with steroid receptor coactivator-1 (SRC-1), co-repressors including silencing mediator for thyroid hormone receptors (SMRT) and nuclear receptor co-repressor (NCoR). BPA exposure resulted in decreased TM4 cell proliferation. BPA inhibited the AR N/C interaction significantly. Furthermore, BPA enhanced the interactions of AR-SMRT and AR-NCoR significantly. In conclusion, these data suggest BPA inhibits Sertoli cell proliferation due to its anti-androgenic actions. The mechanisms responsible for AR antagonism of BPA involve inhibiting the AR N/C interaction and enhancing the interactions of AR-SMRT and AR-NCoR. The data uncover novel anti-androgenic mechanisms by which BPA antagonizes AR signaling, contributing to Sertoli cell proliferation suppression and male reproductive toxicology.

MicroRNA-23b functions as an oncogene and activates AKT/GSK3\u03b2/\u03b2-catenin signaling by targeting ST7L in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a malignant tumor and threatens human life worldwide, whereas the etiology and pathogenesis of HCC have not been fully determined. In the past few years, many microRNAs (miRNAs) have been proved to have important roles in tumorigenesis of HCC. In this study, we found that miR-23b was significantly upregulated in tumor tissues of HCC patients. Functional tests showed that miR-23b could promote HCC cell proliferation and metastasis in vitro and in vivo. Then, mechanistic investigations suggested that ST7L was a direct target of miR-23b and involved in the promotion effects of miR-23b on HCC tumorigenesis and metastasis. Furthermore, our study indicated that ST7L could interact with the carboxyl terminal region of AKT and suppress AKT/GSK3β/β-catenin pathway in HCC cells. In conclusion, our study revealed important roles of miR-23b and ST7L in progression of HCC.

Dimerization in LBD16 and LBD18 Transcription Factors Is Critical for Lateral Root Formation.

LATERAL ORGAN BOUNDARIES DOMAIN/ASYMMETRIC LEAVES2-LIKEs (hereafter referred to as LBD) are plant-specific transcription factors that play important roles in a plethora of plant growth and development. The leucine (Leu) zipper-like coiled-coil motif in the lateral organ boundaries domain of the class I LBD proteins has been proposed to mediate protein dimerization, but it has not been experimentally assessed yet. LBD16 and LBD18 have been well characterized to play important roles in lateral root development in Arabidopsis (Arabidopsis thaliana). Here, we investigated the role of the coiled-coil motif in the dimerization of LBD16 and LBD18 and in transcriptional regulation and biological function. We built the molecular models of the coiled coil of LBD16 and LBD18, providing the probable Leu zipper models of the helix dimer. Using a variety of molecular techniques, such as bimolecular fluorescence complementation, luciferase complementation imaging, GST pull down, and coimmunoprecipitation assays, we showed that the conserved Leu or valine residues in the coiled-coil motif are critical for the dimerization of LBD16 or LBD18. Using transgenic Arabidopsis plants that overexpress HA:LBD16 or HA:LBD16Q in lbd16 or HA:LBD18 or HA:LBD18Q in lbd18, we demonstrated that the homodimerization of LBD18 mediated by the coiled-coil motif is crucial for transcriptional regulation via promoter binding and for lateral root formation. In addition, we found that the carboxyl-terminal region beyond the coiled-coil motif in LBD18 acts as an additional dimerization domain. These results provide a molecular basis for homodimerization and heterodimerization among the 42 Arabidopsis LBD family members for displaying their biological functions.