The Luteinizing Hormone Receptor (LHR) is expressed primarily in the gonads where it mediates signals that regulate ovarian and testicular function. LHR is transcriptional regulated by diverse networks,in which coordination and interactions between regulatory effectors are essential for silencing/activation of LHR expression. The proximal Sp1 site of the promoter recruits histone (H) deacetylases and the Sin3A corepressor complex that contributes to the silencing of LHR transcription. Site specific acetylation/methylation induced by TSA causes phosphatase release that serves as a switch for Sp1 phosphorylation, recruitment of TFIIB and Pol II and transcriptional activation Positive coactivator 4(PC4) is recruited by Sp1, acts as its coactivator and has an essential role in the formation/assembly of PIC and TFIIB and Pol II recruitment in TSA mediated LHR transcription. Our recent studies demonstrated association between PC4 and acetylated H3 in TSA induced LHR derepression in MCF7 cells. MS/MS analysis revealed that PC4 associates with histone variant H3.3 acetylated at several Lys residues. The presence of these modifications was further confirmed by IP of FlagPC4-H3 complex with detection by site specific acetylH3 antibodies in Western blots. ChiP/reChiP analysis showed an increased recruitment of complexes of PC4/acetylated H3 at these sites to the LHR promoter upon TSA stimulation. Further, IP studies with Flag demonstrated interaction of PC4 with H3.3 induced by TSA using H3.3 specific antibody and the presence of the complex PC4-H3.3 at the LHR promoter was demonstrated by reChiP. Depletion of endogenous PC4 or H3.3A/B by siRNA caused marked reduction of TSA induced formation of the complex,its recruitment to the LHR promoter and transcriptional activation of the LHR gene. In recent studies we found that this resulted from a decrease of accessibility of the chromatin at the promoter region of the LHR as indicated by the relative increases of DNAse protection in cells with H3.3 knock-down. Recent pull-down studies demonstrated association of H3/H3.3 with GST-PC4 in MCF7-extracts, while no direct association with H4 was found. Similarly, direct association with recombinant H3 and H3.3 proteins was observed in GST-PC4 pull-down assay indicating direct association with H3 and H3.3 but not H4. Since addition of H3-H4 or H3.3-H4 tetramer revealed H3 and H4 or H3.3 and H4 protein bands, respectively in GST pull-down assay, we conclude that PC4 associates with the tetramer via H3 or H3.3. This is in contrast with findings in Flag-PC4 transfected cells where PC4 associates with endogenous histone proteins but not with the tetramer as evidence by the only presence of H3 and absence of H4 in IP with Flag antibody. This could indicate dissociation of the tetramer resulting from the association with the PC4-SP1 complex. The recruitment of PC4 to SP1 and formation of the PC4-SP1 complex was previously shown to be essential for LHR transcription. PC4 expression is not affected by TSA, therefore PC4 levels do not related to changes in H3/H3.3-Ac. However, PC4-H3.3 interaction favors histone acetylation. Knock-down of endogenous PC4 in MCF7 cells resulted in significant reduction of H3K-acetylated protein expression, TSA induced enrichment of H3K9-Ac and H3.3 at the promoter and consequently of LHR transcriptional activity. Our studies linked acetylation of H3 to PC4 since its absence abolished H3 acetylation induced by TSA despite of major increases in expression of both H3 and H3.3 protein induced by TSA. Acetylation of H3.3 leads to chromatin accessibility and gene transcription. Taken together, these findings indicate a critical role of PC4 association with acetylated H3.3 in TSA-induced Sp1 activated LHR transcription. Gonadotropin regulated Testicular RNA Helicase (GRTH/DDX25), is a testis-specific member of the DEAD-box family of RNA helicases present in Leydig cells (LC) and meiotic germ essential for the completion of spermatogenesis. Males lacking GRTH are sterile due azoospermia resulting from failure of round spermatids to elongate. We demonstrated its participation on the nuclear export/transport of specific mRNAs, the structural integrity of the Chromatoid Body storage/processing of relevant mRNAs and their transit/association to the actively translating polyribosomes where it may regulate translational initiation of genes. GRTH is regulated by LH through androgen (A)/A receptor (AR)at the transcriptional level in LCs (direct)with impact in steroidogenesis, and germ cells (indirect through AR in Sertoli cells) where its expression is both cell-and stage specific. Tg-mice model carrying GRTH 5' flanking regions-GFP generated in our laboratory provided in-vivo systems that permitted differential elucidation of regions in the GRTH gene that directs its expression (upstream) in germ cells and downstream in LCs and its direct regulation by A/AR in LC, and indirectly in germ cells. Functional binding sites for Germ Cell Nuclear Factor (GCNF) present in round spermatids (RS) and spermatocytes(SP) and its regulation by A/AR were identified in the distal region-of the GRTH gene, operative selectively in RS. The studies provided evidence for actions of A on GCNF cell specific regulation of GRTH expression in germ cells. Also, GRTH exerts negative autocrine regulation of GCNF. Our in vivo/in vitro models link A actions to germ cells through GCNF as an A regulated transfactor that controls transcription/expression of GRTH, provided a connection of A action to two relevant germ cell genes essential for the progress of spermatogenesis and established their regulatory interrelationship. Our early studies revealed that missense mutation of R to H at aa 242 of GRTH found in 5.8% of patients with complete loss of sperm causes loss of the 61 kDa cytoplasmic phospho-species with preservation of the non-phospho form. This finding provided an avenue to elucidate the function of phospho-GRTH in spermatogenesis. We generated a humanized mutant GRTH knock-in (KI) mice. Very recent studies revealed that mutant mice are sterile with reduction on testicular size, lack sperm with arrest at step 8 of round spermatids and complete loss of the phospho-GRTH species with preservation of the non phospho-form. This mice model will permit to discern the biological and biochemical impact of the phospho species in GRTH function. In recent studies we elucidated the GRTH phospho-site at a Thr adjacent to the mutant site found in patients. Molecular modelling of the phospho-site based on the DDX19 crystal structure, elucidated the relevant amino acids that formed the GRTH/PKA interface. Studies based on the abolition of the phospho-form provide the basis for drug design, virtual and throughput screening for discovery of a reversible chemical inhibitor for use as male contraceptive. Prolactin receptor mediates the diverse actions of prolactin (PRL) and has important role in the etiology and progression of breast cancer. Our studies have elucidated the relevance of PRL, E2 and its receptor liganded/unliganded, EGF,ERBB1/EGFR and ERBB2/HER2 in upregulation of the PRLR and their mechanistic commonalities for definition of PRL/PRLR induce progression and metastasis of breast tumors, that could explain persistent and invasiveness in certain refractory states to adjuvant endocrine therapies. We have recently demonstrated that the specific CDK7 kinase inhibitor which inhibits E2-induced-phosphorylation of ERa at S118 abrogated E2-induced PRLR transcription/expression and E2-induced cell migration. THZ1 singly or in combination with other approaches targeting PRLR function/signaling, could ablate PRLR transcription/expression and prevent PRLR fueled by tumor PRL deleterious effects in breast cancer.
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