Identification of genes induced by BRCA1 in breast cancer cells

Abstract

Inherited mutations of the BRCA1 gene predispose to cancer of the breast, ovaries and other organs. The BRCA1 protein product is implicated in the maintenance of chromosomal integrity as BRCA1-deficient cells display gross chromosomal rearrangements. Chromosomal instability in BRCA1-deficient cells is related to inappropriate DNA double-strand break repair. The role of the BRCA1 gene in the maintenance of chromosomal integrity is linked to a number of biological properties of its protein product including transcriptional regulation. The aim of this study is to identify genes that are regulated by BRCA1. Initial attempts to overexpress BRCA1 in breast cancer cells with the tightly-regulated ecdysone inducible system did not result in the desired levels of BRCA1 protein and ectopic BRCA1 expression was therefore performed by using the constitutive expression vector. In this study, we have identified genes whose expression levels are upregulated as a result of BRCA1 overexpression in MCF7 breast carcinoma cells by using the suppression subtractive hybridisation (SSH) method. Differential screening, sequencing and homology search studies showed that BRCA1 overexpression in breast cancer cells leads to transcriptional upregulation of distinct classes of genes encoding proteins involved in cellular processes such as DNA repair, chromosome assembly and segregation, signal transduction, RNA surveillance, ubiquitin-mediated proteolysis, amino acid transport, RNA metabolism and glucose metabolism. This study is the first to report BRCA1- induced genes in breast carcinoma cells with the SSH technique. The identified genes in this study may provide new insights into the tumour suppressor functions of BRCA1.