Discovery of a novel long terminal repeat (LTR2i_SS) in Sus Scrofa

Long terminal repeat (LTR) retrotransposons are transposable elements flanked by 5'/3' LTRs. They have a structure similar to endogenous retroviruses, but they lack the envelope (env) gene making them non-infectious. Long terminal repeats are motif-rich sequences and can act as bidirectional promoters or enhancers to regulate or inactivate genes by insertion. In this study, we identified a new chimeric LTR subfamily, LTR2i_SS, in the pig genome. This chimeric LTR family appears to be the ancestral form of the previously described LTR2_SS family. LTR2_SS appears to have deleted ~300 bp of un-annotated, ancestral sequence from LTR2i_SS. We identified no functional provirus sequences for either of these LTR types. LTR2i_SS sequences have been exapted into the untranslated regions of two protein-coding gene mRNAs. Both of these genes lie within previously mapped pig quantitative trait loci.