Involvement of Hus1 in the chain elongation step of DNA replication after exposure to camptothecin or ionizing radiation

• Published in: Nucleic acids research 2004-01, Vol.32 (2), p.767-775
• Main Authors: Wang, Xiang, Guan, Jun, Hu, Baocheng, Weiss, Robert S., Iliakis, George, Wang, Ya
• Format: Article
• Language: English
• Subjects: Animals; Ataxia Telangiectasia Mutated Proteins; Camptothecin - pharmacology; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cells, Cultured; Checkpoint Kinase 1; DNA Replication - drug effects; DNA Replication - radiation effects; DNA-Binding Proteins; Enzyme Activation - drug effects; Enzyme Activation - radiation effects; Fibroblasts; Gene Deletion; Hus1 gene; Mice; Phosphorylation - drug effects; Phosphorylation - radiation effects; Proliferating Cell Nuclear Antigen - metabolism; Protein Kinases - metabolism; Protein Serine-Threonine Kinases - metabolism; Radiation, Ionizing; S Phase - drug effects; S Phase - radiation effects; Schizosaccharomyces pombe Proteins; Tumor Suppressor Proteins
• ISSN: 0305-1048; 1362-4962; 1362-4962
• DOI: 10.1093/nar/gkh243

DNA damage‐induced S phase (S) checkpoint includes inhibition of both replicon initiation and chain elongation. The precise mechanism for controlling the two processes remains unclear. In this study, we showed that Hus1‐deficient mouse cells had an impaired S checkpoint after exposure to DNA strand break‐inducing agents such as camptothecin (CPT) (≥1.0 µM), or ionizing radiation (IR) (≥15 Gy). The Hus1‐dependent S checkpoint contributes to cell resistance to CPT. This impaired S checkpoint induced by CPT or IR in Hus1‐deficient cells reflected mainly the chain elongation step of DNA replication and was correlated with the reduction of dissociation of PCNA from DNA replication foci. Although Hus1 is required for Rad9 phosphorylation following exposure of cells to CPT or IR, Hus1‐deficient cells showed normal activation of ATR/CHK1 and ATM kinases at doses where the checkpoint defects were manifested, suggesting that Hus1 is not a component of the sensor system for activating these pathways in S checkpoint induced by CPT or IR.