Insertion of group II intron retroelements after intrinsic transcriptional terminators.
Mobile DNAs use many mechanisms to minimize damage to their hosts. Here we show that a subclass of group II introns avoids host damage by inserting directly after transcriptional terminator motifs in bacterial genomes (stem-loops followed by Ts). This property contrasts with the site-specific behavior of most group II introns, which insert into homing site sequences. Reconstituted ribonucleo protein particles of the Bacillus halodurans intron B.h.I1 are shown to reverse-splice into DNA targets in vitro but require the DNA to be single-stranded and fold into a stem-loop analogous to the RNA structure that forms during transcription termination. Recognition of this DNA stem-loop motif accounts for in vivo target specificity. Insertion after terminators is a previously unrecognized strategy for a selfish DNA because it prevents interruption of coding sequences and restricts expression of the mobile DNA after integration.
Robart
Aaron R
AR
Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4.
Seo
Wooseok
W
Zimmerly
Steven
S
D001407:Bacillus / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics / Q000502:physiology; D007438:Introns / Q000235:genetics* / Q000502:physiology; D018626:Retroelements / Q000235:genetics* / Q000502:physiology; D013728:Terminator Regions, Genetic / Q000502:physiology; D014158:Transcription, Genetic
D004269:DNA, Bacterial; D018626:Retroelements