Role for poliovirus protease 2A in cap independent translation.

Macadam, Andrew; Ferguson, Geraldine; Fleming, T.P.; Stone, David M.; Almond, Jeffrey W.; Minor, Philip D.

doi:10.1002/j.1460-2075.1994.tb06336.x

Cited by 62 publications

(51 citation statements)

References 22 publications

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“…Although 2A pro proteolytic activity certainly plays a major role, IRES stimulation by a 2A pro active-site mutant incapable of eIF4G cleavage supports transacting functions independent of proteolytic activity. A possible stimulatory role of eIF4G degradation has been ascribed to (i) enhanced efficiency of the C-terminal eIF4G fragment in promoting internal initiation (10,35,38), (ii) IRES repression by intact eIF4G (56), or (iii) translation shutoff of capped messages conveying a competitive advantage to the IRES. Our results do not support a role for 2A…”

Section: Discussionmentioning

confidence: 99%

Competitive Translation Efficiency at the Picornavirus Type 1 Internal Ribosome Entry Site Facilitated by ViralcisandtransFactors

Dobrikova

Grisham

Kaiser

et al. 2006

J Virol

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Enteroviruses (EVs) overcome their host cells by usurping the translation machinery to benefit viral gene expression. This is accomplished through alternative translation initiation in a cap-independent manner at the viral internal ribosomal entry site (IRES). We have investigated the role of cis-and trans-acting viral factors in EV IRES translation in living cells. We observed that considerable portions of the viral genome, including the 5-proximal open reading frame and the 3 untranslated region, contribute to stimulation of IRESmediated translation. With the IRES in proper context, translation via internal initiation in uninfected cells is as efficient as at capped messages with short, unstructured 5 untranslated regions. IRES function is enhanced in cells infected with the EV coxsackievirus B3, but the related poliovirus has no significant stimulatory activity. This differential is due to the inherent properties of their 2A protease and is not coupled to 2A-mediated proteolytic degradation of the eukaryotic initiation factor 4G. Our results suggest that the efficiency of alternative translation initiation at EV IRESs depends on a properly configured template rather than on targeted alterations of the host cell translation machinery.Plus-strand RNA viruses are among the most common human pathogens, responsible for devastating pandemics in the past (poliomyelitis) and present (hepatitis C virus infection and dengue hemorrhagic fever). Upon entering susceptible host cells, positive-strand RNA viruses utilize their genome as a template for viral gene expression in competition with host cell mRNAs for the translation machinery. To accomplish this, many positive-strand RNA viruses alter the host cell protein synthesis apparatus and employ unorthodox translation strategies involving 5Ј untranslated region (5ЈUTR) and 3ЈUTR with uncommon structural features. This is exemplified by the Enterovirus genus of Picornaviridae.Conventional translation of eukaryotic mRNAs occurs upon formation of a ribonucleoprotein network that engages the 43S preinitiation complex (53). This network bridges the 5Ј terminus of eukaryotic mRNAs, universally modified by an m 7 Gppp cap, and a poly(A) tail. Components of the eukaryotic initiation factor 4F (eIF4F) complex mediate template closure: the cap-binding eIF4E binds to eIF4G, which interacts with the poly(A)-binding protein (PABP) (16,43,50). Since it also interacts with the RNA helicase eIF4A and via eIF3 with the 40S ribosomal subunit, eIF4G assumes a central scaffolding function for preinitiation complex assembly (20).Despite their extreme genetic austerity, enteroviruses (EVs) devote a considerable portion of their genomes to elaborate, highly structured 5Ј-and 3ЈUTRs and encode a poly(A) tail of ϳ50 nucleotides (nt) in length. The viral 5ЈUTR contains an internal ribosomal entry site (IRES) mediating 5Ј-end, capindependent translation initiation of the uncapped genome (26, 40). The onset of viral gene expression coincides with severe disruptions of the intracellular milieu, incl...

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Section: Discussionmentioning

confidence: 99%

Competitive Translation Efficiency at the Picornavirus Type 1 Internal Ribosome Entry Site Facilitated by ViralcisandtransFactors

Dobrikova

Grisham

Kaiser

et al. 2006

J Virol

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“…In particular, it neither contains the amino acid residues (catalytic triad) of the putative active site of 2A proteases of rhino-and enteroviruses (Palmenberg, 1990), nor does it share any significant similarity in its C terminus with cardio-and aphthoviruses (Ryan et al, 1991). In addition, lack of p220 inactivation by HAV and thus failure of host cell shut-off (De Chastonay & Siegl, 1987) suggest that 2A of HAV has features distinct from that of poliovirus 2A Macadam et al, 1994). This is consistent with the idea that the diverse functions of a related gene product encoded by different picornaviruses may result from the varied requirements of the virus for growth in different host cells (Kong et al, 1994).…”

Section: Discussionmentioning

confidence: 99%

Identification of hepatitis A virus non-structural protein 2B and its release by the major virus protease 3C

Gosert

Cassinotti

Siegl

et al. 1996

Journal of General Virology

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The RNA genome of hepatitis A virus (HAV) encodes a giant polyprotein that is putatively cleaved proteolytically into four structural and seven non-structural proteins. So far, most of the proposed non-structural proteins and their respective cleavage sites have not been identified. A vaccinia virus recombinant (vRGORF) containing the complete HAV ORF under the control of the bacteriophage T7 promoter was used to express HAY in recombinant animal cells (BT7-H) that constitutively expressed T7 DNA-dependent RNA polymerase. A HAV-specific 27.5 kDa expression product was identified as peptide 2B. The 27.5 kDa 2B antigen was also found in HAV-infected MRC-5 cells. The N-terminal amino acid residues of the new peptide 2B are Ala-Lys-Ile-Ser-Leu-Phe and polyprotein cleavage between 2A and 2B occurred at amino acids 836-837 (Gln-Ala). Furthermore, heterologous expression in the same system of regions P1-P2 and of the protease 3C (3C pr°) gene, showed that P1-P2 polyprotein is not cleaved autocatalytically but by 3C p'°. Hence, 3C vr° is effective in cleaving the polyprotein 2A-2B junction.

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“…The first cleavage occurs in cis, while the polyprotein is still being synthesized on polysomes, separating the precursor of structural protein P1 from 2A pro itself (27). The second 2A promediated cleavage is less efficient and occurs on the 3CD pro precursor to generate two alternative products, 3CЈ and 3DЈ, of still unknown function (28,29 polyprotein processing and cytotoxicity, 2A pro has been implicated in other steps of the poliovirus replicative cycle, such as enhancement of poliovirus mRNA translation and participation in the RNA replication apparatus, and as a determinant of the mouse neurovirulent phenotype (29,(33)(34)(35)(36). It is remarkable that a protein as small as 2A pro (only 149 amino acids) carries out multiple functions during the virus life cycle, perhaps reflecting a common strategy followed by viruses to condense their genetic information.…”

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confidence: 99%