title: Androgen receptor serine 81 phosphorylation mediates chromatin binding and transcriptional activation.
abstract: Our previous findings indicated that androgen receptor (AR) phosphorylation at serine 81 is stimulated by the mitotic cyclin-dependent kinase 1 (CDK1). In this report, we extended our previous study and confirmed that Ser-81 phosphorylation increases during mitosis, coincident with CDK1 activation. We further showed blocking cell cycle at G(1) or S phase did not disrupt androgen-induced Ser-81 phosphorylation and AR-dependent transcription, consistent with a recent report that AR was phosphorylated at Ser-81 and activated by the transcriptional CDK9. To assess the function of Ser-81 phosphorylation in prostate cancer (PCa) cells expressing endogenous AR, we developed a ligand switch strategy using a ligand-binding domain mutation (W741C) that renders AR responsive to the antagonist bicalutamide. An S81A/W741C double mutant AR stably expressed in PCa cells failed to transactivate the endogenous AR-regulated PSA or TMPRSS2 genes. ChIP showed that the S81A mutation prevented ligand-induced AR recruitment to these genes, and cellular fractionation revealed that the S81A mutation globally abrogated chromatin binding. Conversely, the AR fraction rapidly recruited to chromatin after androgen stimulation was highly enriched for Ser-81 phosphorylation. Finally, inhibition of CDK1 and CDK9 decreased AR Ser-81 phosphorylation, chromatin binding, and transcriptional activity. These findings indicate that Ser-81 phosphorylation by CDK9 stabilizes AR chromatin binding for transcription and suggest that CDK1-mediated Ser-81 phosphorylation during mitosis provides a pool of Ser-81 phosphorylation AR that can be readily recruited to chromatin for gene reactivation and may enhance AR activity in PCa.
authors.affiliation: Hematology-Oncology Division, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA. schen@bidmc.harvard.edu
authors.forename: Shaoyong
authors.initials: S
authors.lastname: Chen
authors.forename: Sarah
authors.initials: S
authors.lastname: Gulla
authors.forename: Changmeng
authors.initials: C
authors.lastname: Cai
authors.forename: Steven P
authors.initials: SP
authors.lastname: Balk
mesh_terms: D019943:Amino Acid Substitution; D000728:Androgens / Q000494:pharmacology; D016203:CDC2 Protein Kinase / Q000235:genetics / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D002843:Chromatin / Q000235:genetics / Q000378:metabolism*; D042863:Cyclin-Dependent Kinase 9 / Q000235:genetics / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects / Q000502:physiology; D006801:Humans; D020125:Mutation, Missense; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D016196:S Phase / Q000187:drug effects / Q000502:physiology; D012694:Serine / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*
chemical_list: D000728:Androgens; D002843:Chromatin; D011944:Receptors, Androgen; D012694:Serine; D016203:CDC2 Protein Kinase; C467969:CDK9 protein, human; D042863:Cyclin-Dependent Kinase 9; D012697:Serine Endopeptidases; C421305:TMPRSS2 protein, human