Garvey Tara L, Bertin John, Siegel Richard M, Wang G H, Lenardo Michael J, Cohen Jeffrey I
Medical Virology Section, Laboratory of Clinical Investigation, Molecular Development of the Immune System Section, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892, USA.
J Virol. 2002 Jan;76(2):697-706. doi: 10.1128/jvi.76.2.697-706.2002.
Molluscum contagiosum virus (MCV), a member of the human poxvirus family, encodes the MC159 protein that inhibits Fas-, tumor necrosis factor (TNF)-, and TNF-related apoptosis-inducing ligant (TRAIL)-induced apoptosis. We used site-directed mutagenesis to change charged or hydrophobic amino acid residues to alanines to identify regions of MC159 that are critical for protection from apoptosis and for protein-protein interactions. Surprisingly, while MC159 is thought to block apoptosis by binding to Fas-associated death domain (FADD) or caspase-8, several mutants that lost apoptosis blocking activity still bound to both FADD and caspase-8. Mutations in the predicted hydrophobic patch 1 and alpha2 regions of both death effector domains (DEDs) within MC159 resulted in loss of the ability to bind to FADD or caspase-8 and to block apoptosis. Amino acid substitutions in the RXDL motif located in the alpha6 region of either DED resulted in loss of protection from apoptosis induced by Fas, TNF, and TRAIL and abolished the ability of MC159 to block death effector filament formation. Thus, charged or hydrophobic amino acids in three regions of the MC159 DEDs (hydrophobic patch 1, alpha2, and alpha6) are critical for the protein's ability to interact with cellular proteins and to block apoptosis.
传染性软疣病毒（MCV）是人类痘病毒家族的一员，它编码MC159蛋白，该蛋白可抑制Fas、肿瘤坏死因子（TNF）以及TNF相关凋亡诱导配体（TRAIL）诱导的细胞凋亡。我们利用定点诱变技术将带电荷或疏水性氨基酸残基替换为丙氨酸，以确定MC159中对于保护细胞免受凋亡以及蛋白质-蛋白质相互作用至关重要的区域。令人惊讶的是，尽管人们认为MC159通过与Fas相关死亡结构域（FADD）或半胱天冬酶-8结合来阻断细胞凋亡，但一些丧失凋亡阻断活性的突变体仍能与FADD和半胱天冬酶-8结合。MC159内两个死亡效应结构域（DED）的预测疏水区1和α2区域发生突变，导致其失去与FADD或半胱天冬酶-8结合以及阻断细胞凋亡的能力。位于任一DED的α6区域的RXDL基序中的氨基酸替换，导致丧失对Fas、TNF和TRAIL诱导的细胞凋亡的保护作用，并消除了MC159阻断死亡效应细丝形成的能力。因此，MC159 DEDs的三个区域（疏水区1、α2和α6）中的带电荷或疏水性氨基酸对于该蛋白与细胞蛋白相互作用以及阻断细胞凋亡的能力至关重要。
