BRCA1 and breast cancer: Furthermore, R-loops accumulate in human cells depleted of DNA repair factors that act during replication, such as those involved in the FA/BRCA pathway [77], that is in the tumor suppressor and breast cancer-susceptibility genes BRCA1 and BRCA2 [33,78] or the Fanconi anemia (FA) factors FANCD2, FANCA or FANCM [14,79].