Recruitment of host functions suggests a repair pathway for late steps in group II intron retrohoming.
Retrohoming of group II introns occurs by a mechanism in which the intron RNA reverse splices directly into one strand of a DNA target site and is then reverse transcribed by the associated intron-encoded protein. Host repair enzymes are predicted to complete this process. Here, we screened a battery of Escherichia coli mutants defective in host functions that are potentially involved in retrohoming of the Lactococcus lactis Ll.LtrB intron. We found strong (greater than threefold) effects for several enzymes, including nucleases directed against RNA and DNA, replicative and repair polymerases, and DNA ligase. A model including the presumptive roles of these enzymes in resection of DNA, degradation of the intron RNA template, traversion of RNA-DNA junctions, and second-strand DNA synthesis is described. The completion of retrohoming is viewed as a DNA repair process, with features that may be shared by other non-LTR retroelements.
Smith
Dorie
D
Molecular Genetics Program, Wadsworth Center, New York State Department of Health and School of Public Health, State University of New York at Albany, Albany, New York 12201, USA.
Zhong
Jin
J
Matsuura
Manabu
M
Lambowitz
Alan M
AM
Belfort
Marlene
M
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D011088:DNA Ligases / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair / Q000502:physiology; D004261:DNA Replication / Q000502:physiology; D004251:DNA Transposable Elements / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D007438:Introns / Q000502:physiology*; D012326:RNA Splicing / Q000502:physiology; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D018626:Retroelements / Q000502:physiology*
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; C099786:LtrB protein, Lactococcus lactis; D012329:RNA, Bacterial; D018626:Retroelements; D011088:DNA Ligases