title: Tat-binding protein-1 (TBP-1), an ATPase of 19S regulatory particles of the 26S proteasome, enhances androgen receptor function in cooperation with TBP-1-interacting protein/Hop2.
abstract: The 26S proteasome, which degrades ubiquitinated proteins, appears to contribute to the cyclical loading of androgen receptor (AR) to androgen response elements of target gene promoters; however, the mechanism whereby the 26S proteasome modulates AR recruitment remains unknown. Using yeast two-hybrid screening, we previously identified Tat-binding protein-1 (TBP-1), an adenosine triphosphatase of 19S regulatory particles of the 26S proteasome, as a transcriptional coactivator of thyroid hormone receptor. Independently, TBP-1-interacting protein (TBPIP) was also identified as a coactivator of several nuclear receptors, including AR. Here, we investigated whether TBP-1 could interact with and modulate transcriptional activation by AR cooperatively with TBPIP. TBP-1 mRNA was ubiquitously expressed in human tissues, including the testis and prostate, as well as in LNCaP cells. TBP-1 directly bound TBPIP through the amino-terminal domain possessing the leucine zipper structure. AR is physically associated with TBP-1 and TBPIP in vitro and in LNCaP cells. TBP-1 similarly and additively augmented AR-mediated transcription upon coexpression with TBPIP, and the ATPase domain, as well as leucine zipper structure in TBP-1, was essential for transcriptional enhancement. Overexpression of TBP-1 did not alter AR protein and mRNA levels. In the chromatin immunoprecipitation assay, TBP-1 was transiently recruited to the proximal androgen response element of the prostate-specific antigen gene promoter in a ligand-dependent manner in LNCaP cells. These findings suggest that a component of 19S regulatory particles directly binds AR and might participate in AR-mediated transcriptional activation in cooperation with TBPIP.
authors.affiliation: Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, 3-39-15 Showa-machi, Maebashi, Gunma 371-8511, Japan. tsato@showa.gunma-u.ac.jp
authors.forename: Tetsurou
authors.initials: T
authors.lastname: Satoh
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishizuka
authors.forename: Takuya
authors.initials: T
authors.lastname: Tomaru
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yoshino
authors.forename: Yasuyo
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Koshi
authors.initials: K
authors.lastname: Hashimoto
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Shibusawa
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Monden
authors.forename: Masanobu
authors.initials: M
authors.lastname: Yamada
authors.forename: Masatomo
authors.initials: M
authors.lastname: Mori