Understanding The Function And Regulation of The DNA Polymerase Catalytic Subunit Gene POLD1 in The Human Prostate Carcinoma Cells

• Main Authors: Mei Hsien Lin, 林美嫻
• Other Authors: H. H. Juang
• Format: Others
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/97453949105350418889

碩士 === 長庚大學 === 基礎醫學研究所 === 96 === In Eukaryotes there are five DNA polymerase including alpha, beta, gamma, delta, and epsilon which are responsible for different reactions of DNA synthesis. The 125 kDa subunit (POLD1) of DNA polymerase delta contains the polymerase active site and the active site for the 3’-5’-exonuclease activity. Results from 3H-thymidine incorporation assay and flow cytometric analysis reveal that knock-down POLD1 gene expression attenuates cell proliferation and arrest cell cycle at S phase in human prostate carcinoma PC-3 cells. Using doxorubicin-treated LNCaP cells and p53-overexpresssion PC-3 cells, our study demonstrates that p53 blocks POLD1 gene expression through a consensus p53 response element. Results from reporter assays, immunoblot assays and RT-PCR indicate that R1881, an androgen analog, indirectly blocks the gene expression of POLD1 in LNCaP cells. Gene expression of POLD1 is also modulated by NFκB; however, androgen-sensitivity and androgen-insensitivity prostate carcinoma cells have contrary results. Hypoxia induce cell proliferation may due to the upregulation of POLD1 gene expression in PC-3 cells which is determined by 3H-thymidine incorporation, immunoblot and reporter assays. Stably-overexpression of prostatic specific NKX3.1 homeobox gene or NDRG1 gene in PC-3 cells attenuates cell proliferation and blocks gene expression of POLD1. Forced-overexpression of PDEF (prostate-derived Ets factor) in DU145 cells enhances cell proliferation and upregulates gene expression of POLD1. This study provides the first evidence of the biological mechanism of human POLD1 gene which is important modulator of cell proliferation in the human prostate carcinoma cells; moreover, the gene expression of POLD1 is regulated by androgen, p53, NFκB, HIF-1α, NKX3.1, NDRG1 and PDEF.