RESUMO
Spontaneous mutations in Drosophila melanogaster are related mainly to transposable elements (TEs). They are caused by both migration of TEs over the genome (transpositions) and the ability of TEs to induce chromosomal mutations. Migration of DNA transposons is accompanied by formation of double-strand DNA breaks (DSBs), which are repaired by host repair systems encoded by genes for recombination repair. We relied on this notion to develop a combined approach to the investigation of the type of DNA breaks accompanying transpositions; investigation of systems involved in DSB repair; and detection of repair genes, whose products were involved in repair of DNA breaks induced by TE transposition. The approach is based on the combination of experimental insertional mutagenesis systems and genetic environment deficient for enzymes of the repair system in a single genome. The main advantages of this approach are versatility, wide applicability, and simple design.
Assuntos
Quebras de DNA de Cadeia Dupla , Reparo do DNA , Replicação do DNA , Elementos de DNA Transponíveis , Drosophila melanogaster/genética , Mutagênese Insercional , Animais , MutaçãoRESUMO
Genes coding for the restriction-modification system Fsp4HI, recognizing the sequence 5'-GCNGC-3' have been cloned in Escherichia coli ER2267 cells and its primary structure has been determined. This RM system consists of two genes: the DNA-methyltransferase gene which is followed by the restriction endonuclease gene in the same direction. The analysis of amino acid sequences of the proteins showed that M.Fsp4HI belongs to C5 DNA-methyltransferases, and the restriction enzyme shares more or less significant homology to just a few restriction endonucleases with related recognition sequences. M.Fsp4HI enzyme was purified by means of column chromatography. According to the results of biochemical study it was considered that M.Fsp4HI has its optimal activity at 30 degree C and pH 7.5. M.Fsp4HI modifies the first cytosine residue in the sequence 5'-GCNGC-3'.
Assuntos
Proteínas de Bactérias/genética , Enzimas de Restrição-Modificação do DNA/genética , DNA-Citosina Metilases/genética , Flavobacterium/genética , Sequência de Aminoácidos , Proteínas de Bactérias/química , Clonagem Molecular , Enzimas de Restrição-Modificação do DNA/química , DNA-Citosina Metilases/química , Escherichia coli/genética , Flavobacterium/enzimologia , Dados de Sequência Molecular , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Especificidade por Substrato/genéticaRESUMO
The review presents a description and comparative analysis of the known enzymatic systems of DNA repair in Drosophila melanogaster. Data on protein products, mechanisms of action, and the involvement of the repair system elements in other cellular processes are summarized.