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The SIOD disorder protein SMARCAL1 is an RPA-interacting protein involved in replication fork restart

Howard Hughes Medical Institute and Department of Genetics, Harvard Medical School, Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Genes & development (Impact Factor: 12.64). 09/2009; 23(20):2415-25. DOI: 10.1101/gad.1832309
Source: PubMed

ABSTRACT The integrity of genomic DNA is continuously challenged by the presence of DNA base lesions or DNA strand breaks. Here we report the identification of a new DNA damage response protein, SMARCAL1 (SWI/SNF-related, matrix associated, actin-dependent regulator of chromatin, subfamily a-like 1), which is a member of the SNF2 family and is mutated in Schimke immunoosseous dysplasia (SIOD). We demonstrate that SMARCAL1 directly interacts with Replication protein A (RPA) and is recruited to sites of DNA damage in an RPA-dependent manner. SMARCAL1-depleted cells display sensitivity to DNA-damaging agents that induce replication fork collapse, and exhibit slower fork recovery and delayed entry into mitosis following S-phase arrest. Furthermore, SIOD patient fibroblasts reconstituted with SMARCAL1 exhibit faster cell cycle progression after S-phase arrest. Thus, the symptoms of SIOD may be caused, at least in part, by defects in the cellular response to DNA replication stress.

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    • "DNA fiber analysis after a temporary replication block has revealed that perturbed forks fail to resume DNA synthesis in SMARCAL1-depleted U2OS cells, while new origin firing was unaffected (Ciccia et al. 2009). Recruitment to sites of stalled replication and DNA damage is mediated by SMARCAL1's interaction with single-stranded DNA binding protein RPA, and the absence of SMARCAL1 causes accumulation of spontaneous DNA damage as indicated by activation of the ATM damage response kinase and γH2AX focus formation (Bansbach et al. 2009; Ciccia et al. 2009; Postow et al. 2009; Yuan et al. 2009; Yusufzai et al. 2009). Strikingly, γH2AX focus formation induced in the absence of SMARCAL1 could be almost entirely suppressed by concomitant depletion of MUS81 (Bétous et al. 2012). "
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    • "SMARCAL1 travels with the replisome during an unperturbed S phase (Bé tous et al., 2012) and is concentrated at stalled forks via a direct interaction with RPA (Bansbach et al., 2009; Ciccia et al., 2009; Yuan et al., 2009; Yusufzai et al., 2009). Cells lacking SMARCAL1 are hypersensitive to replication stress (Bansbach et al., 2009; Ciccia et al., 2009; Yuan et al., 2009; Yusufzai et al., 2009) and accumulate DSBs during DNA replication due to fork cleavage by the MUS81 endonuclease (Bé tous et al., 2012). Too much SMARCAL1 activity also causes fork-related damage indicating that SMARCAL1 must be regulated to prevent it from interfering with normal DNA replication (Bansbach et al., 2009). "
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    • "Loss of HARP affects cellular proliferation and differentiation, and the response to replication stress [79]. Following the Kadonaga lab's report, three other labs found similar enzymatic activity for HARP and further defined its biological functions [11] [12] [13]. HARP binds directly to RPA via a conserved N-terminal motif and anneals RPA-coated complementary ssDNA. "
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