BIOL308 Lecture Notes - Lecture 13: Dna Mismatch Repair, Uvrabc Endonuclease, Muts-1
16 Jul 2014
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Mismatch repair removes errors that escape proofreading: corrects errors during replication. Must be rapid - before the next replication round. Distortion of dna backbone enables detection of mismatch. Mismatch repair system - mutgenes of e. coli (5): Muts translocates along dna until a gatc sequence is reached. Binding of muts at the 2 locations creates loop in dna. Muth nicks unmethylated strand of dna (lewin, 2006. Strand is then progressively degraded from gatc to mismatch. In 5"-3" direction or in 3" to 5" direction [using different exonucleases] Gatc sequences occur once every 256 bp [44] except in Dam methylase will methylate the adenine of all gatc sites. However, for a few min after the replication fork passes, newly synthesized dna is still hemimethylated. Once activated by mutsl, muth selectively nicks unmethylated strand. New strand [where the error is] is selectively targeted. Higher eukaryotes possess homologues to mut proteins: replication slippages: mutsa and mutla proteins recognize and repair.
