A variant of the breast cancer type 2 susceptibility protein (BRC) repeat is essential for the RECQL5 helicase to interact with RAD51 recombinase for genome stabilization.

Abstract

The BRC repeat is a structural motif in the tumor suppressor BRCA2 (breast cancer type 2 susceptibility protein), which promotes homologous recombination (HR) by regulating RAD51 recombinase activity. To date, the BRC repeat has not been observed in other proteins, so that its role in HR is inferred only in the context of BRCA2. Here, we identified a BRC repeat variant, named BRCv, in the RECQL5 helicase, which possesses anti-recombinase activity in vitro and suppresses HR and promotes cellular resistance to camptothecin-induced replication stress in vivo. RECQL5-BRCv interacted with RAD51 through two conserved motifs similar to those in the BRCA2-BRC repeat. Mutations of either motif compromised functions of RECQL5, including association with RAD51, inhibition of RAD51-mediated D-loop formation, suppression of sister chromatid exchange, and resistance to camptothecin-induced replication stress. Potential BRCvs were also found in other HR regulatory proteins, including Srs2 and Sgs1, which possess anti-recombinase activities similar to that of RECQL5. A point mutation in the predicted Srs2-BRCv disrupted the ability of the protein to bind RAD51 and to inhibit D-loop formation. Thus, BRC is a common RAD51 interaction module that can be utilized by different proteins to either promote HR, as in the case of BRCA2, or to suppress HR, as in RECQL5.

• Authors: M Nurul Islam, Nicolas Paquet, David Fox 3rd, Eloise Dray, Xiao-Feng Zheng, Hannah Klein, Patrick Sung, Weidong Wang
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 287 Issue 28 Pg. 23808-18 (Jul 06 2012) ISSN: 1083-351X [Electronic] United States
• PMID: 22645136 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Antineoplastic Agents, Phytogenic
• BRCA2 Protein
• RECQL5 protein, human
• Rad51 Recombinase
• RecQ Helicases
• Camptothecin

Topics

• Amino Acid Motifs (genetics)
• Amino Acid Sequence
• Animals
• Antineoplastic Agents, Phytogenic (pharmacology)
• BRCA2 Protein (chemistry, genetics, metabolism)
• Blotting, Western
• Camptothecin (pharmacology)
• Cell Line, Tumor
• DNA Replication (drug effects, genetics)
• Genomic Instability
• HEK293 Cells
• Humans
• Models, Molecular
• Molecular Sequence Data
• Mutation
• Protein Binding
• Protein Structure, Tertiary
• Rad51 Recombinase (chemistry, genetics, metabolism)
• RecQ Helicases (chemistry, genetics, metabolism)
• Recombination, Genetic
• Sequence Homology, Amino Acid