BRCA1 and BRCA2 Gene Expression: Diurnal Variability and Influence of Shift Work

BRCA1 and BRCA2 genes are involved in DNA double-strand break repair and related to breast cancer. Shift work is associated with biological clock alterations and with a higher risk of breast cancer. The aim of this study was to investigate the variability of expression of BRCA genes through the day in healthy subjects and to measure BRCA expression levels in shift workers. The study was approached in two ways. First, we examined diurnal variation of BRCA1 and BRCA2 genes in lymphocytes of 15 volunteers over a 24-hour period. Second, we measured the expression of these genes in lymphocytes from a group of shift and daytime workers. The change in 24-hour expression levels of BRCA1 and BRCA2 genes was statistically significant, decreasing from the peak at midday to the lowest level at midnight. Lower levels for both genes were found in shift workers compared to daytime workers. Diurnal variability of BRCA1 and BRCA2 expression suggests a relation of DNA double-strand break repair system with biological clock. Lower levels of BRCA1 and BRCA2 found in shift workers may be one of the potential factors related to the higher risk of breast cancer.