Analysis of a DNA Damage-Inducible Checkpoint Complex

Project: Research project

Project Details


Project Summary:
The integrity of our genomes is threatened continuously by DNA damage caused by errors generated during
replication, metabolically produced reactive oxygen species, spontaneous depurination, ultraviolet and ionizing
radiation, and exogenous agents. This DNA damage triggers two interdependent cellular responses: 1) the
mobilization of specific DNA repair machinery, which acts to correct the lesion, and 2) the activation of
checkpoint signaling pathways, which induce cell cycle arrest and regulate DNA repair. A key node in the
regulation of both responses is the Rad9-Hus1-Rad1 (911) complex. This heterotrimeric clamp-like complex is
loaded onto DNA at sites of damage, where it activates the ATR-Chk1 checkpoint signaling pathway.
Additionally, in vitro studies show that the 911 complex directly interacts with and stimulates the Base Excision
Repair (BER) machinery. Collectively, these observations indicate that the 911 complex serves as sliding
clamp that orchestrates and integrates checkpoint activation and DNA repair to promote genome stability.
Despite this progress, critical questions remain. First, it is not clear how the 911 complex participates in BER
in intact cells. Second, even though Rad9 is highly phosphorylated, an event important for Rad9-mediated
checkpoint activation, it is not known what kinases phosphorylate Rad9 or how they regulate Rad9 function.
Here we propose three specific aims that will determine how the 911 complex participates in BER in cells, and
will examine how two cell cycle-regulated kinases that bind and phosphorylate Rad9 regulate the function of
Rad9. These studies will combine biochemical, genetic, and cell biology approaches to decipher the molecular
mechanisms whereby the 911 clamp regulates these cellular responses to DNA damage. Thus, these studies
will further our understanding of a complex that plays key roles in maintaining genomic stability and preventing
StatusNot started


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