The evolutionary conservation of the bidirectional activity of the NWC gene promoter in jawed vertebrates and the domestication of the RAG transposon

摘要

AbstractTheRAG-1andRAG-2genes form a recombinase complex that is indispensable for V(D)J recombination, which generates the diversity of immunoglobulins and T-cell receptors. It is widely accepted that the presence ofRAGs in the genomes of jawed vertebrates and other lineages is a result of the horizontal transfer of a mobile genetic element. While a substantial amount of evidence has been gathered that clarifies the nature of theRAGtransposon, far less attention has been paid to the genomic site of its integration in various host organisms. In all genomes of the jawed vertebrates that have been studied to date, theRAGgenes are located in close proximity to theNWCgene. We have previously shown that the promoter of the murineNWCgenes exhibits a bidirectional activity, which may have facilitated the integration and survival of theRAGtransposon in the host genome. In this study, we characterise the promoters of theNWChomologues that are present in the representatives of other jawed vertebrates (H.?sapiens,X.?tropicalisandD.?rerio). We show that the features that are characteristic for promoters as the hosts of a successful transposon integration (in terms of the arrangement, bidirectional and constitutive activity and the involvement of the Zfp143 transcription factor in the promoter regulation) are evolutionarily conserved, which indicates that the presence ofRAGgenes i