Intron homing with limited exon homology. Illegitimate double-strand-break repair in intron acquisition by phage t4.

摘要: The td intron of bacteriophage T4 encodes a DNA endonuclease that initiates homing to cognate intronless alleles by double-strand-break (DSB) repair process. A genetic assay was developed analyze the relationship between exon homology and efficiency. Because models predict exonucleolytic processing cleaved recipient leading homologous strand invasion donor allele, performed in wild-type exonuclease-deficient ( rnh or dexA ) phage. Efficient supported lengths 50 bp greater, whereas more limited led precipitous decline levels. However, extensive one still elevated levels when other completely absent. Analysis these “one-sided” events revealed recombination junctions at ectopic sites microhomology implicated nucleolytic degradation illegitimate DSB T4. Interestingly, efficiency with extremely limiting greatly phage deficient 3′-5′ exonuclease, DexA, suggesting length 3′ tails is major determinant repair. Together, results suggest may provide means which introns can invade sites.