Purification and Identification of a Novel Complex Which Is Involved in Androgen Receptor-Dependent Transcription

Abstract

The androgen receptor (AR) binds to and activates transcription of target genes in response to androgens. In an attempt to isolate cofactors capable of influencing AR transcriptional activity, we used an immunoprecipitation method and identified a 44-kDa protein, designated p44, as a new AR-interacting protein. p44 interacts with AR in the nucleus and with an androgen-regulated homeobox protein (NKX3.1) in the cytoplasm of LNCaP cells. Transient-transfection assays revealed that p44 enhances AR-, glucocorticoid receptor-, and progesterone receptor-dependent transcription but not estrogen receptor- or thyroid hormone receptor-dependent transcription. p44 was recruited onto the promoter of the prostate-specific antigen gene in the presence of the androgen in LNCaP cells. p44 exists as a multiprotein complex in the nuclei of HeLa cells. This complex, but not p44 alone, enhances AR-driven transcription in vitro in a cell-free transcriptional system and contains the protein arginine methyltransferase 5, which acts synergistically with p44 to enhance AR-driven gene expression in a methyltransferase-independent manner. Our data suggest a novel mechanism by which the protein arginine methyltransferase is involved in the control of AR-driven transcription. p44 expression is dramatically enhanced in prostate cancer tissue compared with adjacent benign prostate tissue.

ACKNOWLEDGMENTS

We thank Ann Sutton for her critical editorial review and Lola Lopez for expert assistance in the preparation of the manuscript. We thank Donald J. Tindall for generously providing the human NKX 3.1 cDNA clone.

This work was supported in part by U.S. Department of the Army grant DAMS17-01-1-0097, CaP CURE, Cancer Center Support Core grant CA16672, and SPORE in Prostate Cancer grant CA90270 from the National Cancer Institute, National Institutes of Health.

K. Hosohata and P. Li contributed equally to this work.