Báo cáo sinh học: A conditional-lethal vaccinia virus mutant demonstrates that the I7L gene product is required for virion morphogenesis

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: A conditional-lethal vaccinia virus mutant demonstrates that the I7L gene product is required for virion morphogenesis
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Báo cáo sinh học: " A conditional-lethal vaccinia virus mutant demonstrates that the I7L gene product is required for virion morphogenesis"Virology Journal BioMed Central Open AccessShort reportA conditional-lethal vaccinia virus mutant demonstrates that theI7L gene product is required for virion morphogenesisChelsea M Byrd1 and Dennis E Hruby*1,2Address: 1Molecular and Cellular Biology Program, Oregon State University, 220 Nash Hall, Corvallis, Oregon, 97331 USA and 2Department ofMicrobiology, Oregon State University, 220 Nash Hall, Corvallis, Oregon, 97331 USAEmail: Chelsea M Byrd - cbyrd@sgph.com; Dennis E Hruby* - dhruby@sgph.com* Corresponding authorPublished: 08 February 2005 Received: 07 December 2004 Accepted: 08 February 2005Virology Journal 2005, 2:4 doi:10.1186/1743-422X-2-4This article is available from: http://www.virologyj.com/content/2/1/4© 2005 Byrd and Hruby; licensee BioMed Central Ltd.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract A conditional-lethal recombinant virus was constructed in which the expression of the vaccinia virus I7L gene is under the control of the tetracycline operator/repressor system. In the absence of I7L expression, processing of the major VV core proteins is inhibited and electron microscopy reveals defects in virion morphogenesis subsequent to the formation of immature virion particles but prior to core condensation. Plasmid-borne I7L is capable of rescuing the growth of this virus and rescue is optimal when the I7L gene is expressed using the authentic I7L promoter. Taken together, these data suggest that correct temporal expression of the VV I7L cysteine proteinase is required for core protein maturation, virion assembly and production of infectious progeny.Proteolytic cleavage of precursor proteins is an essential well as the L4R core protein precursor. In this work, weprocess in the life cycle of many viruses, including vac- show that I7L proteinase, in a different inducible mutantcinia virus (VV). The cysteine proteinase encoded by the virus, this one regulated by the tetracycline (TET) opera-VV I7L gene, was originally identified based on a sequence tor/repressor system and driven off of the I7L native pro-comparison with the African Swine Fever virus proteinase moter, is responsible for cleaving the other core proteinand an ubiquitin-like proteinase in yeast [1,2]. We have precursors (p4a and p4b). We also demonstrate thatpreviously shown through trans processing assays that the expression of the I7L gene from its native promoterI7L gene product is capable of cleaving the core protein appears to be important for optimal viral assembly andprecursors p4a, p4b, and p25K at conserved AG/X sites replication.and have used reverse genetics to identify active site resi-dues [3,4]. To determine the role that the I7L proteinase To investigate the role of the I7L proteinase in the viral lifeplays in the VV replication cycle, we report here the con- cycle, an inducible mutant virus was constructed in whichstruction and in vivo analysis of a VV mutant in which the the expression of the I7L gene could be regulated by theexpression of the I7L gene can be conditionally regulated. presence or absence of TET using the components of the bacterial tetracycline operon [6,7]. This system has beenWhile this work was in progress, Ansarah-Sobrinho and shown to be successful in the regulation of the vacciniaMoss [5] published a report demonstrating that the I7L virus G1L [8,9] and A14L [10] genes. A plasmid was con-proteinase, in an inducible mutant virus regulated by the structed containing the tetO just upstream of the I7L openlac operator and driven off of the T7 promoter, was reading frame (ORF) in order to regulate expre ...