MMR is responsible for correction of replication errors as erroneous insertion, deletion and mis-incorporation of nucleotides that can arise during DNA replication and recombination that escape the proofreading activity of a DNA polymerase. The process is initiated by MutSalpha and MutLalpha. MutS homologs first recognize the error in DNA. One of these dimers (MSH2/MSH6) is called MutSalpha and the second (MSH2/MSH3) is called MutSbeta. The first heterodimer preferentially recognizes single base mismatches and small insertion/deletion loops (1-2 bases). The second heterodimer primarily recognizes larger loops (2-10 bases). Then physically interact with MutL, which next activates other proteins that remove the error-bearing DNA strand and synthesize the new one. Mutations in the genes coding human MutS and MutL homologs have been linked with the Lynch syndrome, with high risk of cancer.
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