BRCA1 PROTEIN LEVEL IS NOT AFFECTED BY PEPTIDE GROWTH-FACTORS IN MCF1OA CELL-LINE

The breast cancer susceptibility gene (BRCA1) has been identified as a putative tumor suppressor on chromosome 17. We raised antibody agains t Ring-finger domain of BRCA1, The antibody recognizes a specific BRCA 1 protein doublet of about 220 kD, The majority of BRCA1 protein is lo calized to the nuclear fraction of untreated MCF10A cells. Though BRCA 1 is thought to be a growth suppressor gene, no change in BRCA1 protei n level was found when MCF10A cells were arrested by growth factor dep rivation or stimulation of cell proliferation by re-addition of growth factors, Furthermore the subcellular localization of the BRCA1 protei n does not change throughout the cell cycle, These results suggest tha t BRCA1 may not be directly involved in the regulation of the cell cyc le of breast cancer cell line.