DNA MISMATCH REPAIR CATALYZED BY EXTRACTS OF MITOTIC, POSTMITOTIC, AND SENESCENT DROSOPHILA TISSUES AND INVOLVEMENT OF MEI-9 GENE-FUNCTION FOR FULL ACTIVITY

Extracts of Drosophila embryos and adults have been found to catalyze highly efficient DNA mismatch repair, as well as repair of 1- and 5-bp loops, For mispairs T.G and G.G, repair is nick dependent and is spec ific for the nicked strand of heteroduplex DNA, In contrast, repair of A.A, C.A, G.A, C.T, T.T, and C.C is not nick dependent, suggesting th e presence of glycosylase activities, For nick-dependent repair, the s pecific activity of embryo extracts was similar to that of extracts de rived from the entirely postmitotic cells of young and senescent adult s, Thus, DNA mismatch repair activity is expressed in Drosophila cells during both development and aging, suggesting that there may be a fun ction or requirement for mismatch repair throughout the Drosophila lif e span, Nick-dependent repair was reduced in extracts of animals mutan t for the mei-9 gene, mei-9 has been shown to be required in vivo for certain types of DNA mismatch repair, nucleotide excision repair (NER) , and meiotic crossing over and is the Drosophila homolog of the yeast NER gene rad1.