Hepatitis C Virus Core Protein Interacts with Heterogeneous Nuclear Ribonucleoprotein K

Abstract

Hepatitis C virus (HCV) core protein, a component of viral nucleocapsid, has been shown to modulate cellular and viral promoter activities. To identify potential cellular targets for HCV core protein, a human liver cDNA library was screened for core-interacting proteins using the yeast two-hybrid system. Among the proteins identified was heterogeneous nuclear ribonucleoprotein K (hnRNP K), which has been demonstrated to be a transcriptional regulator. The interaction of HCV core protein with hnRNP K was confirmed by glutathione Stransferase fusion protein binding assay, proteinprotein blotting assay, and coimmunoprecipitation in vitro and in vivo. Additionally, these two proteins were shown to be partially colocalized in the nucleus. The hnRNP K-binding site in HCV core protein was mapped to the region from amino acid residues 25-91, a hydrophilic area near the N terminus. The HCV core proteinbinding domain was located within amino acid residues 250 to 392, which contain the three proline-rich domains, of hnRNP K. Furthermore, HCV core protein relieved the suppression effect of hnRNP K on the activity of the human thymidine kinase gene promoter. The specific binding of HCV core protein to hnRNP K suggests that multiple functions of hnRNP K may be disrupted by the core protein during HCV infection and thus explains, in part, the pathogenesis of HCV.

Immune selection and genetic sequence variation in core and envelope regions of hepatitis C virus

“…It can modulate cellular and viral promoter activities, [31][32][33][34] bind to host RNA helicase to interfere with host RNA translation, and interact with host. 35 Recent data has suggested that HCV core may mediate an immunosupressive effect in vivo. In addition, core can directly bind TNF-␤ receptor and may modify the host response to HCV facilitating persistent infection.…”

Physical and functional interactions between hnRNP K and PRMT family proteins

“…Expression vectors for pSG5.HA.PRMT1, pSG5.HA.CARM1, pSG5.HA.Zac1, pSG5.HA.GRIP1, pSG5.HA.p53, pSG5.HA.hnRNP K, pcDNA3.Flag.hnRNP K, pET3a-HCV Core, pcDNA.HCV Core 1-115 , pSV.AR 0 for the human AR, pHE0 for the human ERa, and Gal4DBD.hnRNP K 338-363 were created as described previously [10][11][12][13]. Arginine to lysine mutant (hnRNP K 5RK) was generated by site directed mutagenesis using wild-type pSG5HA.hnRNP K as the template (Stratagene, USA).…”

“…Expression vector for yeast protein-arginine methyltransferase, RMT1, was a gift from Dr. Stallcup MR (University of Southern California, LA, USA) [14]. Reporter genes MMTV-LUC, EREII-LUC, GK1, and p21-LUC and bacterial expression vectors for GST-Zac1, GST-PRMT1, GST-CARM1, and GST-hnRNP K were described previously [10][11][12][13]15]. …”

Modulation of p53 transcription regulatory activity and post-translational modification by hepatitis C virus core protein

“…Apart from acting as the basic building block of viral nucleocapsid, it also interacts with a variety of cellular factors, interfering with their normal functions (Lai and Ware, 2000;Ray and Ray, 2001). For instance, HCV core protein has been shown to target several cellular transcription factors such as hnRNP K (Hsieh et al, 1998), LZIP (Jin et al, 2000), 14-3-3 (Aoki et al, 2000), p21/WAF1 , and RNA helicase CAPRf (You et al, 1999), resulting in the alterations in the responsive transcription regulatory activities. Moreover, HCV core protein is able to cooperate with ras oncogene in the transformation of rodent fibroblasts under certain conditions (Chang et al, 1998), to influence host cell growth and proliferation through different mechanisms (Aoki et al, 2000;Cho et al, 2001;Erhardt et al, 2002), to promote immortalization of primary human hepatocytes (Ray et al, 2000), and to cause HCC formation at the late stage of transgenic mice (Moriya et al, 1998).…”