Molecular mechanisms of integration site selection by Dictyostelium retrotransponsons

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Retrotransposons amplify by producing DNA copies of their own RNA, which then integrate at new sites in the host cell genome. In gene-dense genomes, the actively replicating retrotransposons cause a constant threat of insertional mutagenesis. The genome of the social amoeba Dictyostelium dis-coideum contains retrotransposons that insert preferentially in the vicinity of tRNA genes to avoid insertional mutagenesis of protein-coding genes. Our previous studies on the retrotransposon TRE5-A suggest that specific interactions between a retrotransposon-encoded protein and subunits of the tRNA gene-specific transcription factor TFIIIB mediate integration upstream of tRNA genes. In this project, we will evaluate the hypothesis that two other tRNA gene-specific retrotransposons in the D. discoideum genome also recognize integration sites by protein-protein contacts with tRNA gene-specific transcription factors. We will investigate retrotransposon TRE3-A, which is phylogenetically related to TRE5-A but integrates in the 3' region of tRNA genes, and DGLT-A, which integrates 5' of tRNA genes similar to TRE5-A but belongs to a different retrotransposon group.