Melanoma Antigen Gene Protein-A11 (MAGE-11) F-box Links the Androgen Receptor NH2-terminal Transactivation Domain to p160 Coactivators

Emily B Askew,Suxia Bai,Andrew T Hnat,John T Minges,Elizabeth M Wilson

doi:10.1074/jbc.m109.065979

Abstract

Androgen-dependent transcriptional activity by the androgen receptor (AR) and its coregulators is required for male reproductive development and function. In humans and other primates, melanoma antigen gene protein-A11 (MAGE-11) is an AR selective coregulator that increases AR transcriptional activity. Here we show that the interaction between AR and MAGE-11 is mediated by AR NH(2)-terminal FXXLF motif binding to a highly conserved MAGE-11 F-box in the MAGE homology domain, and is modulated by serum stimulation of mitogen-activated protein kinase phosphorylation of MAGE-11 Ser-174. The MAGE-11-dependent increase in AR transcriptional activity is mediated by a direct interaction between MAGE-11 and transcriptional intermediary factor 2 (TIF2) through the NH(2)-terminal region of TIF2, and by a MAGE-11 FXXIF motif interaction with an F-box-like region in activation domain 1 of TIF2. The results suggest that MAGE-11 functions as a bridging factor to recruit AR coactivators through a novel FXX(L/I)F motif-F-box interaction paradigm.

Highlights

DECEMBER 11, 2009 VOLUME 284 NUMBER 50 knockouts of androgen receptor (AR) in the human population caused by AR gene mutations result in the androgen insensitivity syndrome, and demonstrate the functional importance of AR in male sex development and maturation (1)
The results suggest that endogenous melanoma antigen gene protein-A11 (MAGE-11) levels are low and cell cycle regulated, which may have hindered our attempts to coimmunoprecipitate endogenous MAGE-11 with AR or transcriptional intermediary factor 2 (TIF2)
We were able to demonstrate that small interfering RNA (siRNA) knockdown of AR, MAGE-11, or TIF2 in CWR-R1 cells decreased the DHT and epidermal growth factor (EGF)-stimulated increase in prostate-specific antigen (PSA), an endogenous AR-regulated gene (Fig. 1E, lower panel)

Summary

Introduction

DECEMBER 11, 2009 VOLUME 284 NUMBER 50 knockouts of AR in the human population caused by AR gene mutations result in the androgen insensitivity syndrome, and demonstrate the functional importance of AR in male sex development and maturation (1). Transcriptional activity of AR⌬120 – 472 was eliminated by V33E, an AR mutation that inhibits AR FXXLF motif binding to MAGE-11 but not to AF2 (16) (Fig. 3B).

Results

Conclusion