Cellular protein modification by poliovirus: the two faces of poly(rC)-binding protein.
During picornavirus infection, several cellular proteins are cleaved by virus-encoded proteinases. Such cleavage events are likely to be involved in the changing dynamics during the intracellular viral life cycle, from viral translation to host shutoff to RNA replication to virion assembly. For example, it has been proposed that there is an active switch from poliovirus translation to RNA replication mediated by changes in RNA-binding protein affinities. This switch could be a mechanism for controlling template selection for translation and negative-strand viral RNA synthesis, two processes that use the same positive-strand RNA as a template but proceed in opposing directions. The cellular protein poly(rC)-binding protein (PCBP) was identified as a primary candidate for regulating such a mechanism. Among the four different isoforms of PCBP in mammalian cells, PCBP2 is required for translation initiation on picornavirus genomes with type I internal ribosome entry site elements and also for RNA replication. Through its three K-homologous (KH) domains, PCPB2 forms functional protein-protein and RNA-protein complexes with components of the viral translation and replication machinery. We have found that the isoforms PCBP1 and -2 are cleaved during the mid-to-late phase of poliovirus infection. On the basis of in vitro cleavage assays, we determined that this cleavage event was mediated by the viral proteinases 3C/3CD. The primary cleavage occurs in the linker between the KH2 and KH3 domains, resulting in truncated PCBP2 lacking the KH3 domain. This cleaved protein, termed PCBP2-DeltaKH3, is unable to function in translation but maintains its activity in viral RNA replication. We propose that through the loss of the KH3 domain, and therefore loss of its ability to function in translation, PCBP2 can mediate the switch from viral translation to RNA replication.
Perera
Rushika
R
Department of Microbiology and Molecular Genetics, School of Medicine, Med Sci B240, University of California, Irvine, CA 92697, USA.
Daijogo
Sarah
S
Walter
Brandon L
BL
Nguyen
Joseph H C
JH
Semler
Bert L
BL
D000086042:3C Viral Proteases; D003546:Cysteine Endopeptidases / Q000502:physiology*; D004268:DNA-Binding Proteins; D006367:HeLa Cells; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D009690:Nucleic Acid Conformation; D017955:Poliovirus / Q000502:physiology*; D014176:Protein Biosynthesis; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D012367:RNA, Viral / Q000096:biosynthesis / Q000737:chemistry; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D014764:Viral Proteins / Q000502:physiology*; D014779:Virus Replication / Q000502:physiology*
D004268:DNA-Binding Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C094604:PCBP1 protein, human; C501903:PCBP2 protein, human; D020033:Protein Isoforms; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D014764:Viral Proteins; D003546:Cysteine Endopeptidases; D000086042:3C Viral Proteases