ORC and the intra-S-phase checkpoint: a threshold regulates Rad53p activation in S phase

K Shimada, P Pasero, SM Gasser - Genes & development, 2002 - genesdev.cshlp.org
K Shimada, P Pasero, SM Gasser
Genes & development, 2002genesdev.cshlp.org
The intra-S-phase checkpoint in yeast responds to stalled replication forks by activating the
ATM-like kinase Mec1 and the CHK2-related kinase Rad53, which in turn inhibit spindle
elongation and late origin firing and lead to a stabilization of DNA polymerases at arrested
forks. A mutation that destabilizes the second subunit of the Origin Recognition Complex,
orc2-1, reduces the number of functional replication forks by 30% and severely
compromises the activation of Rad53 by replication stress or DNA damage in S phase. We …
The intra-S-phase checkpoint in yeast responds to stalled replication forks by activating the ATM-like kinase Mec1 and the CHK2-related kinase Rad53, which in turn inhibit spindle elongation and late origin firing and lead to a stabilization of DNA polymerases at arrested forks. A mutation that destabilizes the second subunit of the Origin Recognition Complex, orc2-1, reduces the number of functional replication forks by 30% and severely compromises the activation of Rad53 by replication stress or DNA damage in S phase. We show that the restoration of the checkpoint response correlates in a dose-dependent manner with the restoration of pre-replication complex formation in G1. Other forms of DNA damage can compensate for the reduced level of fork-dependent signal in the orc2-1 mutant, yet even in wild-type cells, the amount of damage required for Rad53 activation is higher in S phase than in G2. Our data suggest the existence of an S-phase-specific threshold that may be necessary to allow cells to tolerate damage-like DNA structures present at normal replication forks.
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