👤 Naoko Tanese

The HP1 family of evolutionarily conserved proteins regulates heterochromatin packaging, in addition to a less defined role in the regulation of euchromatic genes. To examine the possible role of HP1 proteins in fetal prostate development and prostate cancer the protein expression of HP1alpha, beta and gamma was evaluated in human archival tissue. Tissue sections from human prostate cancer and fetal prostate were examined using antibodies against HP1 isoforms to evaluate HP1 modulation in cancer and development. Western blot analysis of HP1 proteins was also performed in extracts of cultured prostate cancer cells. HP1alpha, beta and gamma are differentially regulated in various cellular compartments in prostate development. HP1alpha is not expressed at 14 or 24 weeks of prostate development but it is expressed in adult prostate tissue. HP1beta is highly expressed at 14 and 24 weeks, and it appears predominantly in epithelial cells compared to HP1gamma, which is expressed at equal levels in epithelial and stromal cells. All 3 HP1 isoforms show altered expression in prostate cancer compared to that in normal adult prostate tissue. HP1 proteins are tightly regulated during prostate development. In the adult prostate HP1alpha, beta and gamma antibodies detect high levels of HP1 antigen in a contiguous layer of epithelial cells. However, the detection of HP1 in prostate cancer ranges from undetectable to inconsistent staining of noncontiguous epithelial cells. Show less

The general transcription factor TFIID facilitates recruitment of the transcription machinery to gene promoters and regulates initiation of transcription by RNA polymerase II. hTAF(II)130, a component of TFIID, interacts with and serves as a coactivator for multiple transcriptional regulatory proteins, including Sp1 and CREB. A yeast two-hybrid screen has identified an interaction between hTAF(II)130 and heterochromatin protein 1 (HP1), a chromatin-associated protein whose function has been implicated in gene silencing. We find that hTAF(II)130 associates with HP1 in an isoform-specific manner: HP1alpha and HP1gamma bind to hTAF(II)130, but not HP1beta. In addition, we show that endogenous hTAF(II)130 and components of TFIID in HeLa nuclear extracts associate with glutathione S-transferase-HP1alpha and -HP1gamma. hTAF(II)130 possesses a pentapeptide HP1-binding motif, and mutation of the hTAF(II)130 HP1 box compromises the interaction of hTAF(II)130 with HP1. We demonstrate that Gal4-HP1 proteins interfere with hTAF(II)130-mediated activation of transcription. Our results suggest that HP1alpha and HP1gamma associate with hTAF(II)130 to mediate repression of transcription, supporting a new model of transcriptional repression involving a specific interaction between a component of TFIID and chromatin. Show less