Single-stranded DNA-binding protein hSSB1 is critical for genomic stability

Derek J. Richard, Emma Bolderson, Liza Cubeddu, Ross I. M. Wadsworth, Kienan Savage, Girdhar G. Sharma, Matthew L. Nicolette, Sergie Tsvetanov, Michael J. McIlwraith, Raj K. Pandita, Shunichi Takeda, Ronald T. Hay, Jean Gautier, Stephen C. West, Tanya T. Paull, Tej K. Pandita, Malcolm F. White, Kum Kum Khanna

    Research output: Contribution to journalArticlepeer-review

    203 Citations (Scopus)


    Single- strand DNA ( ssDNA)- binding proteins ( SSBs) are ubiquitous and essential for a wide variety of DNA metabolic processes, including DNA replication, recombination, DNA damage detection and repair(1). SSBs have multiple roles in binding and sequestering ssDNA, detecting DNA damage, stimulating nucleases, helicases and strand- exchange proteins, activating transcription and mediating protein - protein interactions. In eukaryotes, the major SSB, replication protein A ( RPA), is a heterotrimer(1). Here we describe a second human SSB ( hSSB1), with a domain organization closer to the archaeal SSB than to RPA. Ataxia telangiectasia mutated ( ATM) kinase phosphorylates hSSB1 in response to DNA double- strand breaks ( DSBs). This phosphorylation event is required for DNA damage- induced stabilization of hSSB1. Upon induction of DNA damage, hSSB1 accumulates in the nucleus and forms distinct foci independent of cell- cycle phase. These foci co-localize with other known repair proteins. In contrast to RPA, hSSB1 does not localize to replication foci in S- phase cells and hSSB1 deficiency does not influence S- phase progression. Depletion of hSSB1 abrogates the cellular response to DSBs, including activation of ATM and phosphorylation of ATM targets after ionizing radiation. Cells deficient in hSSB1 exhibit increased radiosensitivity, defective checkpoint activation and enhanced genomic instability coupled with a diminished capacity for DNA repair. These findings establish that hSSB1 influences diverse end-points in the cellular DNA damage response.

    Original languageEnglish
    Pages (from-to)677-U13
    Number of pages6
    Issue number7195
    Publication statusPublished - 29 May 2008


    • S-PHASE
    • DAMAGE
    • ATM


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