B1-SINE retrotransposons

Abstract

More than half the size of most mammalian genomes is composed by repetitive sequences. Short Interspersed Nuclear Element (SINE) retrotransposons constitute one of the main components of the genomic repetitive fraction. The abundance and evolutionary conservation of these sequences support their contribution to maintain the stability and proper function of the genome. Several recent studies have unveiled some of these intriguing tasks, which include, but are not limited to the control of transcriptional regulation and the organization of the chromatin. Here, we will comment on our recent report characterizing the insulator/boundary activity of a novel B1 SINE retrotransposon (B1-X35S) widely present in the mouse genome. A remarkable finding was that B1-X35S-dependent insulation required not only the combinatorial binding of transcription factors dioxin receptor (AhR) and Snai2/Slug, but also a molecular switch between RNA Polymerases (Pol) Pol III and Pol II. Moreover, B1-X35S seemingly forms heterochroma...