Human single-stranded DNA binding protein 1 (hSSB1/NABP2) is required for the stability and repair of stalled replication forks

Abstract

Aberrant DNA replication is a primary cause of mutations that are associated with pathological disorders including cancer. During DNA metabolism, the primary causes of replication fork stalling include secondary DNA structures, highly transcribed regions and damaged DNA. The restart of stalled replication forks is critical for the timely progression of the cell cycle and ultimately for the maintenance of genomic stability. Our previous work has implicated the single-stranded DNA binding protein, hSSB1/NABP2, in the repair of DNA double-strand breaks via homologous recombination. Here, we demonstrate that hSSB1 relocates to hydroxyurea (HU)-damaged replication forks where it is required for ATR and Chk1 activation and recruitment of Mre11 and Rad51. Consequently, hSSB1-depleted cells fail to repair and restart stalled replication forks. hSSB1 deficiency causes accumulation of DNA strand breaks and results in chromosome aberrations observed in mitosis, ultimately resulting in hSSB1 being required for survival to HU and camptothecin. Overall, our findings demonstrate the importance of hSSB1 in maintaining and repairing DNA replication forks and for overall genomic stability.

Ssb1 and Ssb2 cooperate to regulate mouse hematopoietic stem and progenitor cells by resolving replicative stress

“…[3][4][5][6][7][8] Our generation and phenotypic analysis of cDKO mice has unmasked the compensatory and essential functions of Ssb1/Ssb2 in maintaining tissue homeostasis, which was unexpected from analysis of single knockout mouse models.…”

“…Depletion of SSB1 in cells results in increased radiosensitivity, defective repair of DNA double-strand breaks (DSBs), oxidative DNA damage, and failure to restart stalled replication forks. [3][4][5][6][7][8] Moreover, Ssb1 has been shown to regulate telomere homeostasis by protecting newly replicated G-overhangs of leading-and lagging-strand telomeres. 9,10 SSB1 is recurrently mutated in various cancers, and an SSB2/RARA fusion gene has been described in variant acute promyelocytic leukemia.…”

The MRE11–RAD50–NBS1 Complex Conducts the Orchestration of Damage Signaling and Outcomes to Stress in DNA Replication and Repair

“…This uncoupling results in long stretches of ssDNA, leading to an ATR checkpoint response that helps to stabilize the fork and allows time to resolve the replication barrier by arresting cell cycle progression (Figure 4) (121). Stretches of ssDNA are protected by ssDNA-binding proteins such as RPA or human single-stranded DNA binding protein 1 (hSSB1) (130, 131). RPA binding to ssDNA inhibits annealing of short homologous sequences (as in short repeats) through microhomology-mediated repair and reduces secondary structures recognized by nucleases (132).…”

Novel insight into the composition of human single-stranded DNA-binding protein 1 (hSSB1)-containing protein complexes

“…Previous studies have suggested that both of these proteins function as mutually exclusive components of the sensor of single-stranded DNA (SOSS) complex in partnership with the integrator complex subunit 3 (INTS3) and hSSB-interacting protein 1 (hSSBIP1; SOSSC) [16–19]. The depletion of any of these proteins has further been demonstrated to increase the sensitivity of cells to DNA damage caused by ionising radiation exposure and treatment with the topoisomerase I inhibitor, camptothecin [17, 20, 21]. Here, hSSB1 has been reported to stimulate resection of double-strand DNA break ends by the Mre11-Nbs1-Rad50 (MRN) [22, 23] and Exo1 [24] nucleases, as well as activation of the ATM kinase [20].…”