Phosphorylated hMSH6: DNA mismatch versus DNA damage recognition.

ABSTRACT: DNA mismatch repair (MMR) maintains genomic integrity by correction of mispaired bases and insertion-deletion loops. The MMR pathway can also trigger a DNA damage response upon binding of MutS? to specific DNA lesions such as O(6)methylguanine (O(6)meG). Limited information is available regarding cellular regulation of these two different pathways. Within this report, we demonstrate that phosphorylated hMSH6 increases in concentration in the presence of a G:T mismatch, as compared to an O(6)meG:T lesion. TPA, a kinase activator, enhances the phosphorylation of hMSH6 and binding of hMutS? to a G:T mismatch, though not to O(6)meG:T. UCN-01, a kinase inhibitor, decreases both phosphorylation of hMSH6 and binding of hMutS? to G:T and O(6)meG:T. HeLa MR cells, pretreated with UCN-01 and exposed to MNNG, undergo activation of Cdk1 and mitosis despite phosphorylation of Chk1 and inactivating phosphorylation of Cdc25c. These results indicate that UCN-01 may inhibit an alternative cell cycle arrest pathway associated with the MMR pathway that does not involve Cdc25c. In addition, recombinant hMutS? containing hMSH6 mutated at an N-terminal cluster of four phosphoserines exhibits decreased phosphorylation and decreased binding of hMutS? to G:T and O(6)meG:T. Taken together, these results suggest a model in which the amount of phosphorylated hMSH6 bound to DNA is dependent on the presence of either a DNA mismatch or DNA alkylation damage. We hypothesize that both phosphorylation of hMSH6 and total concentration of bound hMutS? are involved in cellular signaling of either DNA mismatch repair or MMR-dependent damage recognition activities.

SUBMITTER: Kaliyaperumal S 

PROVIDER: S-EPMC3010429 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature