Poly(C)-binding protein interacts with the hepatitis C virus 5' untranslated region.

Abstract

We have investigated whether poly(C)-binding protein (PCBP)-1 and PCBP-2 interact with the hepatitis C virus (HCV) 5h untranslated region. Our results demonstrate that glutathione Stransferase (GST)-PCBP-1 and GST-PCBP-2 fusion proteins bind specifically to the HCV 5h untranslated region. An antiserum raised against PCBP-2 induced a supershift after incubation with RNA-protein complexes formed between proteins in a HeLa cell cytoplasmic extract and the HCV 5h untranslated region, indicating that this interaction occurs intracellularly. The complete internal ribosome entry site was necessary for efficient binding, suggesting that maintenance of the secondary structure was necessary for recognition of the binding site by the PCBPs.

HuR Displaces Polypyrimidine Tract Binding Protein To Facilitate La Binding to the 3′ Untranslated Region and Enhances Hepatitis C Virus Replication

“…The cellular proteins that are necessary for HCV IRES-mediated translation and replication have been identified through small interfering RNA (siRNA) knockdown screens and other independent studies. Some of these proteins, such as the human La autoantigen (La) (5,6), polypyrimidine tract binding protein (PTB) (5), heterogeneous nuclear ribonucleoprotein Q (hnRNPQ) (7), hnRNPL (8), poly(C)-binding protein 2 (PCBP2) (9), and ribosomal protein S5 (RPS5) (10), have been shown to modulate HCV translation by binding to the HCV IRES. Also, the competition between La protein and the viral NS3 protease for binding to the IRES has been shown to regulate the translation-replication switch in HCV (11).…”

The poly(C)-binding proteins: A multiplicity of functions and a search for mechanisms

“…The role of aCP-2 in translational enhancement may be shared by other picornaviruses+ Cap-independent translation initiation within the picornavirus family is mediated by two major classes of IRESs (type I and type II)+ These IRESs differ in their sequences, secondary structures, and biological properties (Wimmer et al+, 1993;Ehrenfeld, 1996)+ The enteroviruses and rhinoviruses utilize type I IRESs, and the cardioviruses and aphthoviruses utilize the type II IRES elements+ Although aCP-2 is capable of interacting in vitro with both type I IRESs (from coxsackievirus strain B and human rhinovirus) and type II IRES (from encephalomyocarditis virus and foot-and-mouth disease virus), an effect on translation of the cardiovirus and aphthovirus has not been demonstrated+ These data suggest that a functional role for aCP-2 in binding to viral 59 UTRs appears to be limited to type I IRES elements (Walter et al+, 1999)+ aCP plays a role in the translation of viruses in addition to those in the picornavirus family+ Although the IRES element of hepatitis A virus (HAV) cannot easily be classified as a type I or type II IRES (Brown et al+, 1994), aCP-2 is required to facilitate HAV internal ribosome entry similarly to type I IRESs (Graff et al+, 1998)+ Along the same lines, the hepatitis C virus (HCV) IRES has been difficult to classify as a type I or type II IRES due to its unique structure (Reynolds et al+, 1995)+ Whereas aCP-1 and aCP-2 can bind specifically to the HCV 59 UTR (Spangberg & Schwartz, 1999), it has not been possible to document an effect of this binding on HCV translation (Fukushi et al+, 2001)+ In this respect, the HAV IRES behaves in a manner reminiscent of a type I IRES, whereas HCV IRES resembles a type II IRES+ Thus, aCP binding can contribute to both silencing and enhancement of translation+ The former action is mediated by 39 UTR complexes and the latter by complexes within the 59 IRES segments of picornaviruses+ In neither case are the downstream events that control the rates of ribosome loading clearly defined+ In both cases, the complexes are formed at substantial distances from the sites of translation initiation+ Whether the two processes converge on a common pathway remains an interesting possibility+ Delineation of the 274…”

A Hepatitis C Virus cis -Acting Replication Element Forms a Long-Range RNA-RNA Interaction with Upstream RNA Sequences in NS5B

“…Polyprotein translation is initiated within a highly structured internal ribosome entry site (IRES) occupying much of the 5Ј noncoding region (5Ј NCR). The 5Ј NCR also contains sequences required for genome replication (9,19,26), and like functionally analogous regions in the 3Ј NCR, these form defined stem-loop structures that operate in cis and are known or suspected to recruit cellular or viral proteins (5,10,30). In addition to these cis-acting replication elements (CREs) in the noncoding extremes of the genome, there is evidence that additional RNA structures exist within the coding regions.…”