BCCIP regulates homologous recombination by distinct domains and suppresses spontaneous DNA damage

Abstract

Homologous recombination (HR) is critical for maintaining genome stability through precise repair of DNA double-strand breaks (DSBs) and restarting stalled or collapsed DNA replication forks. HR is regulated by many proteins through distinct mechanisms. Some proteins have direct enzymatic roles in HR reactions, while others act as accessory factors that regulate HR enzymatic activity or coordinate HR with other cellular processes such as the cell cycle. The breast cancer susceptibility gene BRCA2 encodes a critical accessory protein that interacts with the RAD51 recombinase and this interaction fluctuates during the cell cycle. We previously showed that a BRCA2- and p21-interacting protein, BCCIP, regulates BRCA2 and RAD51 nuclear focus formation, DSB-induced HR and cell cycle progression. However, it has not been clear whether BCCIP acts exclusively through BRCA2 to regulate HR and whether BCCIP also regulates the alternative DSB repair pathway, non-homologous end joining. In this study, we found that BCCIP fragments that interact with BRCA2 or with p21 each inhibit DSB repair by HR. We further show that transient down-regulation of BCCIP in human cells does not affect non-specific integration of transfected DNA, but significantly inhibits homology-directed gene targeting. Furthermore, human HT1080 cells with constitutive down-regulation of BCCIP display increased levels of spontaneous single-stranded DNA (ssDNA) and DSBs. These data indicate that multiple BCCIP domains are important for HR regulation, that BCCIP is unlikely to regulate non-homologous end joining, and that BCCIP plays a critical role in resolving spontaneous DNA damage.

Distinct RAD51 Associations with RAD52 and BCCIP in Response to DNA Damage and Replication Stress

“…BCCIP knockdown by siRNA also reduces BRCA2 and RAD51 focus formation, reduces HR repair of DSBs, and causes the accumulation of spontaneous DNA damage (25,26). These results indicate a critical role for BCCIP in BRCA2-and RAD51-dependent HR (25,26).…”

“…The human BRCA2-DBD has been shown to bind DSS1, BUBR1, ABP-280/filamin-A, and BCCIP (22)(23)(24). Importantly, BCCIP binding to BRCA2 facilitates RAD51 nuclear focus formation and HR repair of DSBs (25,26).…”

A DIGE approach for the assessment of differential expression of the CHO proteome under sodium butyrate addition: Effect of Bcl‐xL overexpression

“…In addition, IQGAP1 expression was significantly decreased when apoptosis was induced by anti-tumor reagents in a human hepatoma cell line (Zhou et al, 2009), while overexpression of IQGAP1 enhanced proliferation of epithelial cells (Jadeski et al, 2008), suggesting that up-regulation of IQGAP1 is related to cell survival enhanced by Bcl-x L overexpression. BCCIP, also named Tok-1, plays a critical role in resolving spontaneous DNA damage (Lu et al, 2007). Up-regulation of BCCIP by Bcl-x L overexpression may also contribute to cell survival by reducing DNA damage.…”

LYRIC/AEG-1 overexpression modulates BCCIPα protein levels in prostate tumor cells

“…Using yeast two-hybrid and mammalian cells, we identified BCCIP as an interaction partner for LYRIC/AEG-1, and suggest a direct association between the two proteins. Relatively little is known about BCCIPα, but studies to date demonstrate roles in cell cycle regulation [8,9,12,20], homologous recombination repair [10,21] and cytokinesis [11].…”