Tip60 Is a Nuclear Hormone Receptor Coactivator

Abstract

The androgen receptor (AR) is a member of the nuclear hormone receptor superfamily. Recent work in this field has been focused upon defining the mechanisms of transcriptional control exacted by members of this superfamily. Using a COOH-terminal region of the human AR in a yeast two-hybrid screen, we have identified Tip60 as an AR-interacting protein. In this report, we show that Tip60, which was originally identified as a coactivator for the human immunodeficiency virus TAT protein, can enhance AR-mediated transactivation in a ligand-dependent manner in LNCaP and COS-1 cell lines. In addition, our experiments show that Tip60 can also enhance transactivation through the estrogen receptor and progesterone receptor in a ligand-dependent manner; thus identifying Tip60 as a nuclear hormone receptor coactivator. Our studies also demonstrate that Tip60 co-immunoprecipitates with the full-length AR in vitro and that, in our system, Tip60 enhances transactivation to levels observed with the coactivators steroid receptor coactivator 1, p300, and CREB-binding protein.The importance of such proteins in enhancing nuclear hormone receptor-mediated transcriptional activation is widely accepted, and this work suggests that Tip60 may have an equally important role to play. The AR1 is a member of the nuclear hormone receptor superfamily of ligand-dependent transcription factors. In the nucleus, the ligand-activated receptors bind to their cognate response elements in or near promoter regions of target genes to positively or negatively regulate gene expression (reviewed in Ref.

Expression of Tip60, an androgen receptor coactivator, and its role in prostate cancer development

“…We previously demonstrated that Tip60 interacts directly with the AR and enhances its androgen-induced transcriptional activity (Brady et al, 1999). The distribution pattern and the expression levels of this coactivator in prostate tissue have not yet been addressed.…”

“…FHL2 is an AR-specific co-activator expressed in prostatic epithelium (Muller et al, 2000). We previously identified Tat interactive protein, 60 kDa (Tip60) as an AR coactivator and showed that it potentiates AR transcriptional activity both in vitro and in vivo (Brady et al, 1999). We further demonstrated that Tip60 is a coactivator specific for Class I nuclear hormone receptors, including oestrogen and progesterone receptor (Gaughan et al, 2001).…”

“…SDM was made as previously described (Brady et al, 1999). AI cells were derived from LNCaP cells following continuous passaging in an environment deprived of androgens for a period of 8 months.…”

“…Sample preparation, electrophoretic separation and Western blotting were performed as described (Brady et al, 1999).…”

Pre-clinical evaluation of cyclin-dependent kinase 2 and 1 inhibition in anti-estrogen-sensitive and resistant breast cancer cells

“…Cells were transfected with the E2F reporter construct (200 ng) (Hofman et al, 2001) together with the b-galactosidase construct (200 ng) (Brady et al, 1999) using FuGENE6 transfection reagent (Roche Diagnostics, Lewes, UK) and treated as indicated in figure legends. Luciferase activity was determined after addition of 50 ml luciferase reagent (Promega, Southampton, UK) using a microplate luminometer (Perkin-Elmer, Beaconsfield, UK).…”