B. Cousineau et al., RETROHOMING OF A BACTERIAL GROUP-II INTRON - MOBILITY VIA COMPLETE REVERSE SPLICING, INDEPENDENT OF HOMOLOGOUS DNA RECOMBINATION, Cell (Cambridge), 94(4), 1998, pp. 451-462
The mobile group II intron of Lactococcus lactis, LI.LtrB, provides th
e opportunity to analyze the homing pathway in genetically tractable b
acterial systems. Here, we show that LI.LtrB mobility occurs by an RNA
-based retrohoming mechanism in both Escherichia coli and L. lactis. S
urprisingly, retrohoming occurs efficiently in the absence of RecA fun
ction, with a relaxed requirement for flanking exon homology and witho
ut coconversion of exon markers. These results lead to a model for bac
terial retrohoming in which the intron integrates into recipient DNA b
y complete reverse splicing and serves as the template for cDNA synthe
sis. The retrohoming reaction is completed in unprecedented fashion by
a DNA repair event that is independent of homologous recombination be
tween the alleles. Thus, LI.LtrB has many features of retrotransposons
, with practical and evolutionary implications.