TAILIEUCHUNG - Báo cáo khoa học: Adaptation of intronic homing endonuclease for successful horizontal transmission

Group I introns are thought to be self-propagating mobile elements, and are distributed over a wide range of organisms through horizontal trans-mission. Intron invasion is initiated through cleavage of a target DNA by a homing endonuclease encoded in an open reading frame (ORF) found within the intron. The intron is likely of no benefit to the host cell and is not maintained over time, leading to the accumulation of mutations after intron invasion. | ềFEBS Journal Adaptation of intronic homing endonuclease for successful horizontal transmission Sayuri Kurokawa1 Yoshitaka Bessho2 Kyoko Higashijima2 Mikako Shirouzu2 3 Shigeyuki Yokoyama2 3 4 Kazuo I. Watanabe5 and Takeshi Ohama1 1 Graduate Schoolof Engineering Department of EnvironmentalSystems Engineering Kochi University of Technology KUT Kochi Japan 2 RIKEN Genomic Sciences Center Tsurumi Yokohama Japan 3 RIKEN Harima Institute at SPring-8 Mikazuki-cho Sayo Hyogo Japan 4 Graduate Schoolof Science University of Tokyo Bunkyo Tokyo Japan 5 Institute for Cellular and Molecular Biology The University of Texas at Austin Austin TX USA Keywords I-CsmI Chlamydomonas smithii horizontal transmission group I intron selfish element Correspondence T. Ohama Department of Environmental Systems Engineering Kochi University of Technology KUT Tosayamada Kochi 782-8502 Japan Fax 81 887 572520 Tel 81 887 572512 E-mail Received 10 January 2005 revised 26 February 2005 accepted 18 March 2005 doi Group I introns are thought to be self-propagating mobile elements and are distributed over a wide range of organisms through horizontal transmission. Intron invasion is initiated through cleavage of a target DNA by a homing endonuclease encoded in an open reading frame ORF found within the intron. The intron is likely of no benefit to the host cell and is not maintained over time leading to the accumulation of mutations after intron invasion. Therefore regular invasional transmission of the intron to a new species at least once before its degeneration is likely essential for its evolutionary long-term existence. In many cases the target is in a proteincoding region which is well conserved among organisms but contains ambiguity at the third nucleotide position of the codon. Consequently the homing endonuclease might be adapted to overcome sequence polymorphisms at the target site. To address whether codon degeneracy affects .

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