Regulation of Hepatitis C Virus Polyprotein Processing by Signal Peptidase Involves Structural Determinants at the p7 Sequence Junctions

Institut de Biologie de Lille, Lille, Nord-Pas-de-Calais, France
Journal of Biological Chemistry (Impact Factor: 4.57). 11/2004; 279(40):41384-92. DOI: 10.1074/jbc.M406315200
Source: PubMed


The hepatitis C virus genome encodes a polyprotein precursor that is co- and post-translationally processed by cellular and viral proteases to yield 10 mature protein products (C, E1, E2, p7, NS2, NS3, NS4A, NS4B, NS5A, and NS5B). Although most cleavages in hepatitis C virus polyprotein precursor proceed to completion during or immediately after translation, the cleavages mediated by a host cell signal peptidase are partial at the E2/p7 and p7/NS2 sites, leading to the production of an E2p7NS2 precursor. The sequences located immediately N-terminally of E2/p7 and p7/NS2 cleavage sites can function as signal peptides. When fused to a reporter protein, the signal peptides of p7 and NS2 were efficiently cleaved. However, when full-length p7 was fused to the reporter protein, partial cleavage was observed, indicating that a sequence located N-terminally of the signal peptide reduces the efficiency of p7/NS2 cleavage. Sequence analyses and mutagenesis studies have also identified structural determinants responsible for the partial cleavage at both the E2/p7 and p7/NS2 sites. Finally, the short distance between the cleavage site of E2/p7 or p7/NS2 and the predicted transmembrane alpha-helix within the P' region might impose additional structural constraints to the cleavage sites. The insertion of a linker polypeptide sequence between P-3' and P-4' of the cleavage site released these constraints and led to improved cleavage efficiency. Such constraints in the processing of a polyprotein precursor are likely essential for hepatitis C virus to post-translationally regulate the kinetics and/or the level of expression of p7 as well as NS2 and E2 mature proteins.

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Available from: Laurence Cocquerel, Apr 07, 2014
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    • "During translation of the polyprotein, appropriate signal sequences target the two glycoproteins to the endoplasmic reticulum (ER) where they are released from the polyprotein by the action of the host signal peptidase. This ER enzyme is oriented in the lumen and cleaves the Core-E1, E1-E2 and E2-p7 junctions [8], [9]. In the ER, HCV envelope proteins acquire 4-5 and 11 N-linked glycosylation chains for E1 and E2, respectively, and remain anchored to the membrane through their hydrophobic C-terminal domains. "
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    • "Published online in Wiley InterScience ( mediated by a cellular signal peptidase [Lin et al., 1994; Mizushima et al., 1994; Carrere-Kremer et al., 2004]. However, it is not known whether p7 is a structural or a non-structural protein and whether or not it is associated with HCV particles. "
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