hSSB1 rapidly binds at the sites of DNA double-strand breaks and is required for the efficient recruitment of the MRN complex.
hSSB1 is a newly discovered single-stranded DNA (ssDNA)-binding protein that is essential for efficient DNA double-strand break signalling through ATM. However, the mechanism by which hSSB1 functions to allow efficient signalling is unknown. Here, we show that hSSB1 is recruited rapidly to sites of double-strand DNA breaks (DSBs) in all interphase cells (G1, S and G2) independently of, CtIP, MDC1 and the MRN complex (Rad50, Mre11, NBS1). However expansion of hSSB1 from the DSB site requires the function of MRN. Strikingly, silencing of hSSB1 prevents foci formation as well as recruitment of MRN to sites of DSBs and leads to a subsequent defect in resection of DSBs as evident by defective RPA and ssDNA generation. Our data suggests that hSSB1 functions upstream of MRN to promote its recruitment at DSBs and is required for efficient resection of DSBs. These findings, together with previous work establish essential roles of hSSB1 in controlling ATM activation and activity, and subsequent DSB resection and homologous recombination (HR).
Signal Transduction Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland 4029, Australia. derekr@qimr.edu.au
Derek J
DJ
Richard
Kienan
K
Savage
Emma
E
Bolderson
Liza
L
Cubeddu
Sairei
S
So
Mihaela
M
Ghita
David J
DJ
Chen
Malcolm F
MF
White
Kerry
K
Richard
Kevin M
KM
Prise
Giuseppe
G
Schettino
Kum Kum
KK
Khanna
D017766:Acid Anhydride Hydrolases; D018797:Cell Cycle Proteins / Q000032:analysis; D002460:Cell Line; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000032:analysis; D004268:DNA-Binding Proteins / Q000032:analysis / Q000502:physiology*; D006801:Humans; D000076228:MRE11 Homologue Protein; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins / Q000032:analysis; D011839:Radiation, Ionizing
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; D024101:Mitochondrial Proteins; C112156:NBN protein, human; D009687:Nuclear Proteins; C504091:NABP2 protein, human; D000076228:MRE11 Homologue Protein; D017766:Acid Anhydride Hydrolases; C112158:RAD50 protein, human; D045643:DNA Repair Enzymes