Alternative DNA Damage Checkpoint Pathways in Eukaryotes.

摘要

CHES1 (checkpoint suppressor 1) is sufficient to restore the DNA damage-induced G2 arrest in S. cerevisiae checkpoint mutants (Pati et al, 1997). Our data suggest that Ches1 functions in an alternative checkpoint pathway. Our goals are to identify genes constituting this pathway, to isolate the human counterparts, and to compare their structure and activity in normal and cancer tissues. In order to identify the genes involved in the alternative checkpoint pathway, we mutagenized a checkpoint-deficient strain expressing CHES1. Mutagenized colonies exhibiting checkpoint phenotypes in the presence of CHES1 were further characterized, and represent mutations in genes involved in DNA recombination and repair, gene silencing, microtubule stability, and protein phosphorylation status. We identified proteins that interact with a functional GST-Ches1 fusion protein. The assay revealed Sin3, a component of the Sin3/Rpd3 histone deacetylase complex. Deleting either SIN3 or RPD3 in checkpoint mutants mimics the suppressive effects observed when CHES1 is expressed in checkpoint mutant strains containing wild-type SIN3 or RPD3. In addition, we screened a human fetal brain library via the two-hybrid approach and identified SKIP, which associates with histone deacetylase complexes in human cells. These data suggests that Ches1 may function similarly in yeast and mammalian cells by acting through a histone deacetylation.