title: Interaction between conjugative and retrotransposable elements in horizontal gene transfer.
abstract: Mobile genetic elements either encode their own mobilization machineries or hijack them from other mobile elements. Multiple classes of mobile elements often coexist within genomes and it is unclear whether they have the capacity to functionally interact and even collaborate. We investigate the possibility that molecular machineries of disparate mobile elements may functionally interact, using the example of a retrotransposon, in the form of a mobile group II intron, found on a conjugative plasmid pRS01 in Lactococcus lactis. This intron resides within the pRS01 ltrB gene encoding relaxase, the enzyme required for nicking the transfer origin (oriT) for conjugal transmission of the plasmid into a recipient cell. Here, we show that relaxase stimulates both the frequency and diversity of retrotransposition events using a retromobility indicator gene (RIG), and by developing a high-throughput genomic retrotransposition detection system called RIG-Seq. We demonstrate that LtrB relaxase not only nicks ssDNA of its cognate oriT in a sequence- and strand-specific manner, but also possesses weak off-target activity. Together, the data support a model in which the two different mobile elements, one using an RNA-based mechanism, the other using DNA-based transfer, do functionally interact. Intron splicing facilitates relaxase expression required for conjugation, whereas relaxase introduces spurious nicks in recipient DNA that stimulate both the frequency of intron mobility and the density of events. We hypothesize that this functional interaction between the mobile elements would promote horizontal conjugal gene transfer while stimulating intron dissemination in the donor and recipient cells.
authors.affiliation: Department of Biological Sciences and RNA Institute, University at Albany, Albany, New York, United States of America.
authors.forename: Olga
authors.initials: O
authors.lastname: Novikova
authors.affiliation: Department of Biological Sciences and RNA Institute, University at Albany, Albany, New York, United States of America.
authors.forename: Dorie
authors.initials: D
authors.lastname: Smith
authors.affiliation: Department of Biomedical Sciences, University at Albany, Wadsworth Center, NYS Department of Health, Albany, New York, United States of America.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Hahn
authors.affiliation: Department of Biomedical Sciences, University at Albany, Wadsworth Center, NYS Department of Health, Albany, New York, United States of America.
authors.forename: Arthur
authors.initials: A
authors.lastname: Beauregard
authors.affiliation: Department of Biological Sciences and RNA Institute, University at Albany, Albany, New York, United States of America.
authors.forename: Marlene
authors.initials: M
authors.lastname: Belfort
mesh_terms: D001483:Base Sequence; D003227:Conjugation, Genetic / Q000502:physiology*; D004277:DNA, Single-Stranded / Q000378:metabolism; D004722:Endoribonucleases / Q000502:physiology; D004843:Epistasis, Genetic; D022761:Gene Transfer, Horizontal; D007438:Introns / Q000235:genetics; D013294:Lactococcus lactis / Q000235:genetics*; D030781:Organisms, Genetically Modified; D012326:RNA Splicing / Q000235:genetics; D018626:Retroelements / Q000502:physiology*
chemical_list: D004277:DNA, Single-Stranded; D018626:Retroelements; D004722:Endoribonucleases