CHANGES IN BRCA2 EXPRESSION DURING PROGRESSION OF THE CELL-CYCLE

It has been shown that genetic alterations in BRCA1 and BRCA2 can pred ispose an individual to develop breast cancer. We investigated the exp ression of both BRCA2 and BRCA1 during the progression of the cell cyc le by northern blot analysis. In MCF-10F (normal breast epithelial cel l line) and MCF-7 (breast cancer cell line) cells the expression of BR CA2 RNA was low in G0 and early G1 phases then up-regulated at the G1/ S phase junction. Expression of BRCA2 was maintained at relatively hig h levels when cells progressed through S and G2/M phases. For MCF-7 ce lls, the level of BRCA2 transcript decreased as cells were released fr om nocodazole-mediated metaphase arrest. This is consistent with the o bservation of low but detectable BRCA2 RNA level in G1 phase of the ce ll cycle. For both cell lines, the patterns of RNA expression of BRCA1 and BRCA2 were similar during the proliferation phase of cell cycle. However, the transcripts from both genes were undetectable in quiescen t cells. These results suggest important functions for both BRCA2 and BRCA1 in regulation of cell growth. (C) 1997 Academic Press.