MiRNA regulation of homologous recombination (HR) repair factors after IR. After double strand break (DSB) recognition, BRCA1 (black arrow, pointing up) is phosphorylated by Chk2 kinase and an endonuclease CtIP is delivered for promotion end resection. While, at a later step of HR, BRCA1 recruits PALB2, which mediates promotion of BRCA2 to arrangement on the DNA template. Active BRCA2 (black arrow, pointing up) proteins displaces replication protein A (RPA) in order to load RAD51 onto the DNA. However, low BRCA2 protein levels cause increased levels of RAD52, which promote RAD51 for accurate homologous recombination (HR) repair in BRCA2-deficient cells. The lack of BRCA2 and RAD52 (black arrow, pointing down) causes the most severe genome defects. Major components of the HR pathway are arranged in a scheme based on the aspect of the miRNA regulation post-IR.