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Host processing of branched DNA intermediates is involved in targeted transposition of IS 911
Author(s) -
Loot Celine,
Turlan Catherine,
Chandler Michael
Publication year - 2004
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03850.x
Subject(s) - biology , holliday junction , transposition (logic) , dna , insertion sequence , sequence (biology) , dna replication , genetics , dna repair , transposable element , gene , mutant , computer science , artificial intelligence
Summary A simplified system using bacterial insertion sequence IS 911 has been developed to investigate targeted insertion next to DNA sequences resembling IS ends. We show here that these IR‐targeted events occur by an unusual mechanism. In the circular IS 911 transposition intermediate the two IRs are abutted to form an IR/IR junction. IR‐targeted insertion involves transfer of a single end of the junction to the target IR to generate a branched DNA structure. The single‐end transfer (SET) intermediate, but not the final insertion product, can be detected in an in vitro reaction. SET intermediates must be processed by the bacterial host to obtain the final insertion products. Sequence analysis of these IR‐targeted insertion products and of those obtained in vivo revealed high levels of DNA sequence conversion in which mutations from one IR were transferred to another. These sequence changes cannot be explained by the classic transposition pathway. A model is presented in which the four‐way Holliday‐like junction created by SET is processed by host‐mediated branch migration, resolution, repair and replication. This pathway resembles those described for processing other branched DNA structures such as stalled replication forks.