%0 Journal Article
%T Inherent promoter bidirectionality facilitates maintenance of sequence integrity and transcription of parasitic DNA in mammalian genomes
%A Paul Kalitsis
%A Richard Saffery
%J BMC Genomics
%D 2009
%I BioMed Central
%R 10.1186/1471-2164-10-498
%X The current study provides evidence that many CpG island-associated promoters associated with single genes exhibit inherent bidirectionality, facilitating "hijack" by transposable elements to create novel antisense 'head-to-head' bidirectional gene pairs in the genome that facilitates escape from host-mediated epigenetic silencing. This is often associated with an increase in CpG island length and transcriptional activity in the antisense direction. From a list of over 60 predicted protein-coding genes derived from transposable elements in the human genome and 40 in the mouse, we have found that a significant proportion are orientated in a bidirectional manner with CpG associated regulatory regions.These data strongly suggest that the selective force that shields endogenous CpG-containing promoter from epigenetic silencing can extend to exogenous foreign DNA elements inserted in close proximity in the antisense orientation, with resulting transcription and maintenance of sequence integrity of such elements in the host genome. Over time, this may result in "domestication" of such elements to provide novel cellular and developmental functions.The emergence of novel gene functions is an essential driving force behind the evolution of species. Many molecular mechanisms have been described that contribute to this process including gene duplication, exon shuffling, retroposition, transposable element insertion, lateral (horizontal) gene transfer, and gene fusion/fission events [1].One of these mechanisms, transposable or mobile elements, are segments of DNA encoding genes that assist in DNA excision, replication and integration of the elements into new regions of the genome. Until recently transposable elements (TEs) have been considered parasitic or selfish DNAs that contribute little to the host organism [2,3]. These elements generally exist as neutrally evolving inactive DNA remnants that are epigenetically silenced by the host genome to prevent transcription and subse
%U http://www.biomedcentral.com/1471-2164/10/498