tailieunhanh - Báo cáo y học: " Transposons that clean up after themselves"

Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Minireview cung cấp cho các bạn kiến thức về ngành y đề tài: Transposons that clean up after themselves | Minireview Transposons that clean up after themselves Douglas L Chalker Address Biology Department Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA. Email dchalker@ Published 15 June 2009 GenomeBiology 2009 10 224 doi gb-2009-10-6-224 The electronic version of this article is the complete one and can be found online at http 2009 10 6 224 2009 BioMed Central Ltd Abstract A transposon in the germline genome of the ciliate Oxytricha uses its transposase to remove itself as well as other germline-limited DNA from the differentiating somatic genome during development. The genomes of eukaryotes are littered with transposon-derived sequences. As much as 45 of the human genome is composed of various types of mobile DNA elements or their remnants 1 and in plants such as maize more than 60 of the genome consists of such repetitive sequences 2 . The ability of transposons to take over large chunks of genomes has given them the reputation of being selfish elements only interested in their own propagation. The fact that movement of these sequences into genes can inactivate genes and cause disease 3 is further evidence that they are up to no good. But can sequences that make up such a large fraction of genomes be all bad It is quite possible that mobile DNAs have positive influences on genomes that outweigh their deleterious effects 4 . Transposons do provide novel sequences that can be exploited by their host cells. Several examples are known of transposon functions that have been domesticated that is a once-foreign sequence has been co-opted to carry out a host process reviewed in 5 . For example what was once probably some element s transposase the enzyme that mediates the movement into and out of DNA is now the mammalian Rag1 2 recombinase. This domestication event spurred the innovation of immunoglobulin gene rearrangement and the advent of the vertebrate adaptive immune system. The Rag1 2 proteins .