학술논문

CtIP-mediated resection is essential for viability and can operate independently of BRCA1.
Document Type
article
Source
Journal of Experimental Medicine. 211(6)
Subject
Animals
B-Lymphocytes
BRCA1 Protein
Carrier Proteins
Cell Cycle Proteins
Cell Proliferation
Cell Survival
Cells
Cultured
Chromosomal Proteins
Non-Histone
DNA Breaks
Double-Stranded
DNA Repair
DNA-Binding Proteins
Enzyme Inhibitors
Genomic Instability
Homologous Recombination
Immunoblotting
Mice
Mice
Knockout
Mice
Transgenic
Microscopy
Confocal
Mutation
Poly(ADP-ribose) Polymerase Inhibitors
Poly(ADP-ribose) Polymerases
Protein Binding
Tumor Suppressor p53-Binding Protein 1
Language
Abstract
Homologous recombination (HR) is initiated by DNA end resection, a process in which stretches of single-strand DNA (ssDNA) are generated and used for homology search. Factors implicated in resection include nucleases MRE11, EXO1, and DNA2, which process DNA ends into 3 ssDNA overhangs; helicases such as BLM, which unwind DNA; and other proteins such as BRCA1 and CtIP whose functions remain unclear. CDK-mediated phosphorylation of CtIP on T847 is required to promote resection, whereas CDK-dependent phosphorylation of CtIP-S327 is required for interaction with BRCA1. Here, we provide evidence that CtIP functions independently of BRCA1 in promoting DSB end resection. First, using mouse models expressing S327A or T847A mutant CtIP as a sole species, and B cells deficient in CtIP, we show that loss of the CtIP-BRCA1 interaction does not detectably affect resection, maintenance of genomic stability or viability, whereas T847 is essential for these functions. Second, although loss of 53BP1 rescues the embryonic lethality and HR defects in BRCA1-deficient mice, it does not restore viability or genome integrity in CtIP(-/-) mice. Third, the increased resection afforded by loss of 53BP1 and the rescue of BRCA1-deficiency depend on CtIP but not EXO1. Finally, the sensitivity of BRCA1-deficient cells to poly ADP ribose polymerase (PARP) inhibition is partially rescued by the phospho-mimicking mutant CtIP (CtIP-T847E). Thus, in contrast to BRCA1, CtIP has indispensable roles in promoting resection and embryonic development.