Identifying Deubiquitinase Regulating the DNA Damage Response Pathway.

In response to DNA damage, cells often activate Mec1-dependent DNA damage checkpoint, resulting in the activation of the effector kinase Rad53 that promotes cell cycle arrest and DNA repair. The checkpoint proteins and the DNA damage response pathway are often regulated by ubiquitination, a reversible post-translational modification, raising the possibility that checkpoint activation may be regulated by a deubiquitinating enzyme. To test this, we screened a collection of yeast deubiquitinating enzyme deletion mutants and monitored their responses to DNA damage agents. Interestingly, we find that one deubiquitinating enzyme deletion mutant displayed consistently decreased levels of checkpoint activation. Further analysis indicated that this mutant does not affect either the abundance or the stability of checkpoint activators, but it rather has a profound effect on Mec1 itself. This analysis suggests deubiquitinating enzyme as a novel regulator for Mecl1 and DNA damage checkpoint pathway.