tailieunhanh - Báo cáo khoa học: Ribonuclease H: properties, substrate specificity and roles in retroviral reverse transcription

Retroviral reverse transcriptases possess both a DNA polymerase and an RNase H activity. The linkage with the DNA polymerase activity endows the retroviral RNases H with unique properties not found in the cellular counterparts. | MINIREVIEW Ribonuclease H properties substrate specificity and roles in retroviral reverse transcription James J. Champoux and Sharon J. Schultz Department of Microbiology University of Washington Seattle WA USA Keywords catalytic mechanism DMA RNA hybrids endonuclease human immunodeficiency virus type 1 Moloney murine leukemia virus polypurine tract reverse transcriptase reverse transcription RNA cleavage RNase H Correspondence J. J. Champoux Department of Microbiology Box 357242 University of Washington Seattle WA 98195 USA Fax 1 206 543 8297 Tel 1 206 543 8574 E-mail champoux@ Retroviral reverse transcriptases possess both a DNA polymerase and an RNase H activity. The linkage with the DNA polymerase activity endows the retroviral RNases H with unique properties not found in the cellular counterparts. In addition to the typical endonuclease activity on a DNA7 RNA hybrid cleavage by the retroviral enzymes is also directed by both DNA 3 recessed and RNA 5 recessed ends and by certain nucleotide sequence preferences in the vicinity of the cleavage site. This spectrum of specificities enables retroviral RNases H to carry out a series of cleavage reactions during reverse transcription that degrade the viral RNA genome after minus-strand synthesis precisely generate the primer for the initiation of plus strands facilitate the initiation of plus-strand synthesis and remove both plus- and minus-strand primers after they have been extended. Received 17 October 2008 accepted 12 December 2008 doi At the time of its discovery in 1970 the presence of an RNA-dependent DNA polymerase activity in retrovirus particles provided strong and exciting support for the hypothesis that the single-stranded RNA genome of a retrovirus is replicated through a DNA intermediate 1 2 . Not only did this discovery of reverse transcriptase as it was dubbed challenge the existing dogma concerning the flow of genetic information in biology it raised .

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