Characterization of human BRCA2 truncations on Rad51 levels and homology directed repair in mammalian cells
Two keystone proteins in the homology-directed repair (HDR) pathway for restoring double-stranded DNA breaks are BRCA2 and Rad51, which interact through eight highly conserved motifs known as BRC repeats. Germline mutations in BRCA2 increase the risk of developing early onset cancer, such as 6174delT which truncates BRCA2 within the 7th BRC repeat. Mouse hybridoma cells expressing 2XMBP-tagged human BRCA2 truncated after the 8th, 6th, 4th and just before the 1st repeat, were used to investigate how the number of BRC repeats in a shortened BRCA2 protein impacts Rad51 protein levels. HDR, cell growth, DNA damage tolerance and p53 protein levels were also characterized, with each BRCA2 truncation producing a unique cellular response. The variable effects observed by changing the number of BRC repeats in the context of a missing C-terminal domain underscores the complexity of BRCA2, both in its role in promoting HDR and how dysfunctional proteins lead to tumorigenesis.