Phosphorylation of replication protein A by S-phase checkpoint kinases

NBS1 mediates ATR-dependent RPA hyperphosphorylation following replication-fork stall and collapse

“…Members of the phosphoinositide 3-kinase related kinases (PIKKs) -ATM, DNA-PK and ATR -have been reported to hyperphosphorylate RPA. Each of these kinases has been shown to phosphorylate RPA in vitro and in vivo (Barr et al, 2003;Brush et al, 1994;Gately et al, 1998;Liu et al, 2006;Oakley et al, 2001;Unsal-Kacmaz and Sancar, 2004;Wang et al, 2001). Recent reports have demonstrated ATM-dependent activation of ATR in response to IR, and ATR-dependent activation of ATM in response to HU and UV (Jazayeri et al, 2006;Stiff et al, 2006).…”

Role of RPA Proteins in Radiation Repair and Recovery

“…Xu, et al, 2008). This model is further supported by studies describing a ssDNA length-dependent activation of ATR via RPA (J. S. Liu, et al, 2006;Zou & Elledge, 2003). Activated ATR initiates the intra-S phase checkpoint signal cascade resulting in cell-cycle arrest, stabilization of replication forks, and initiation of damage repair through phosphorylation of effector molecules, including the checkpoint kinase Chk1 (Cimprich & Cortez, 2008;Kastan & Bartek, 2004;Yang, et al, 2003).…”

“…When the replicative helicase is uncoupled from the replisome, large tracts of ssDNA are formed. In eukaryotes this lengthy ssDNA is rapidly coated with RPA, which serves as a signal of replication stress to activate the S phase checkpoint kinase ATR (ATM and Rad3-related), a member of the phosphatidylinositol 3-kinase-like kinase (PIKK) family (Byun, et al, 2005;J. S. Liu, et al, 2006;Zou & Elledge, 2003).…”

“…Specifically, RPA2 is phosphorylated at two consensus sites for Cdc2/Cdk2, resulting in three forms of RPA: unphosphorylated, and two distinct phosphorylated forms (Iftode, et al, 1999;J. S. Liu, et al, 2006;Oakley, et al, 2003;Wold, 1997;Zernik-Kobak, et al, 1997).…”

The Coordination between DNA Replication Initiation and Other Cell Cycle Events

“…Although the mechanism for this checkpoint and the substrates of ATR/CHK1 are poorly understood, the ATR/CHK1-dependent CDK2-cyclin E/cyclin A inhibition through Cdc25A degradation at least partially contributes to the slow down of the overall replication rates. Many DNA replication proteins at the replication forks including RPC (replication factor C complex), RPA1/2, the MCM2-7 complex, MCM10 and several DNA polymerases are phosphorylated by ATR (Cortez, Glick andElledge 2004, Liu, Kuo andMelendy 2006); however, the functions of these phosphorylation events are largely unclear. Besides the checkpoints in response to DNA damage mentioned above, the "S-M checkpoint" is also an intrinsic mechanism required for normal cell cycle progression.…”