title: Transposable element derived DNaseI-hypersensitive sites in the human genome.
abstract: BACKGROUND
  Transposable elements (TEs) are abundant genomic sequences that have been found to contribute to genome evolution in unexpected ways. Here, we characterize the evolutionary and functional characteristics of TE-derived human genome regulatory sequences uncovered by the high throughput mapping of DNaseI-hypersensitive (HS) sites.
  
  
  RESULTS
  Human genome TEs were found to contribute substantially to HS regulatory sequences characterized in CD4+ T cells: 23% of HS sites contain TE-derived sequences. While HS sites are far more evolutionarily conserved than non HS sites in the human genome, consistent with their functional importance, TE-derived HS sites are highly divergent. Nevertheless, TE-derived HS sites were shown to be functionally relevant in terms of driving gene expression in CD4+ T cells. Genes involved in immune response are statistically over-represented among genes with TE-derived HS sites. A number of genes with both TE-derived HS sites and immune tissue related expression patterns were found to encode proteins involved in immune response such as T cell specific receptor antigens and secreted cytokines as well as proteins with clinical relevance to HIV and cancer. Genes with TE-derived HS sites have higher average levels of sequence and expression divergence between human and mouse orthologs compared to genes with non TE-derived HS sites.
  
  
  CONCLUSIONS
  The results reported here support the notion that TEs provide a specific genome-wide mechanism for generating functionally relevant gene regulatory divergence between evolutionary lineages.
  
  
  METHODS
  This article was reviewed by Wolfgang J. Miller (nominated by Jerzy Jurka), Itai Yanai and Mikhail S.Gelfand.
authors.affiliation: National Center for Biotechnology Information, National Institutes of Health, Bethesda, MD 20894, USA. marino@ncbi.nlm.nih.gov
authors.forename: Leonardo
authors.initials: L
authors.lastname: Mariño-Ramírez
authors.forename: I King
authors.initials: IK
authors.lastname: Jordan