Hepatitis C Virus Core Protein Binds to a DEAD Box RNA Helicase

Approximately 4 million Americans are infected with the hepatitis C virus (HCV), making it a major cause of chronic liver disease. Because of the lack of an efficient cell culture system, little is known about the interaction between HCV and host cells. We performed a yeast two-hybrid screen of a human liver cell cDNA library with HCV core protein as bait and isolated the DEAD box protein DBX. DBX has significant amino acid sequence identity to mouse PL10, an ATP-dependent RNA helicase. The binding of DBX to HCV core protein occurred in an in vitro binding assay in the presence of 1 m NaCl or detergent. When expressed in mammalian cells, HCV core protein and DBX were co-localized at the endoplasmic reticulum. In a mutant strain of Saccharomyces cerevisiae, DBX complemented the function of Ded1p, an essential DEAD box RNA helicase. HCV core protein inhibited the growth of DBX-complemented mutant yeast but not Ded1p-expressing yeast. HCV core protein also inhibited the in vitro translation of capped but not uncapped RNA. These findings demonstrate an interaction between HCV core protein and a host cell protein involved in RNA translation and suggest a mechanism by which HCV may inhibit host cell mRNA translation. Approximately 4 million Americans are infected with the hepatitis C virus (HCV), making it a major cause of chronic liver disease. Because of the lack of an efficient cell culture system, little is known about the interaction between HCV and host cells. We performed a yeast two-hybrid screen of a human liver cell cDNA library with HCV core protein as bait and isolated the DEAD box protein DBX. DBX has significant amino acid sequence identity to mouse PL10, an ATP-dependent RNA helicase. The binding of DBX to HCV core protein occurred in an in vitro binding assay in the presence of 1 m NaCl or detergent. When expressed in mammalian cells, HCV core protein and DBX were co-localized at the endoplasmic reticulum. In a mutant strain of Saccharomyces cerevisiae, DBX complemented the function of Ded1p, an essential DEAD box RNA helicase. HCV core protein inhibited the growth of DBX-complemented mutant yeast but not Ded1p-expressing yeast. HCV core protein also inhibited the in vitro translation of capped but not uncapped RNA. These findings demonstrate an interaction between HCV core protein and a host cell protein involved in RNA translation and suggest a mechanism by which HCV may inhibit host cell mRNA translation. Hepatitis C virus (HCV) 1The abbreviations used are: HCV, hepatitis C virus; GST, glutathione S-transferase; GPD, glyceraldehyde-3-phosphate; PCR, polymerase chain reaction1The abbreviations used are: HCV, hepatitis C virus; GST, glutathione S-transferase; GPD, glyceraldehyde-3-phosphate; PCR, polymerase chain reactionwas discovered by cDNA cloning in 1989 and shown to cause chronic liver disease (1Choo Q.-L. Kuo G. Weiner A.J. Overby L.R. Bradley D.W. Houghton M. Science. 1989; 244: 359-362Crossref PubMed Scopus (6209) Google Scholar, 2Kuo G. Choo Q.-L. Alter H.J. Gitnick G.L. Redeker A.G. Purcell R.H. Miyamura T. Dienstag J.L. Alter M.J. Stevens C.E. Tegtmeier G.E. Bonino F. Colombo M. Lee W.-S. Kou C. Berger K. Shuster J.R. Overby R. Bradley D.W. Houghton M. Science. 1989; 244: 362-364Crossref PubMed Scopus (3030) Google Scholar). Approximately 4 million Americans and 150 million individuals worldwide are infected with HCV and at risk for cirrhosis and hepatocellular carcinoma (3Alter M.J. Semin. Liver Dis. 1995; 15: 5-14Crossref PubMed Scopus (484) Google Scholar, 4Mansell C.J. Locarnini S.A. Semin. Liver Dis. 1995; 15: 15-32Crossref PubMed Scopus (109) Google Scholar, 5Mamiya N. Worman H.J. Curr. Opin. Infect. Dis. 1997; 10: 3990-3997Crossref Scopus (1) Google Scholar, 6National Institutes of Health Consensus Development Panel Hepatology. 1997; 26: 1S-156SPubMed Google Scholar). Because development of a robust cell culture system for HCV infection has remained elusive (6National Institutes of Health Consensus Development Panel Hepatology. 1997; 26: 1S-156SPubMed Google Scholar), extremely little is known about HCV-host cell interactions and how they influence cell physiology or viral replication.HCV is a positive single-stranded RNA virus and a member of theFlaviviridae family (1Choo Q.-L. Kuo G. Weiner A.J. Overby L.R. Bradley D.W. Houghton M. Science. 1989; 244: 359-362Crossref PubMed Scopus (6209) Google Scholar, 7Kato N. Hijikata M. Ootsuyama Y. Nakagawa M. Ohkoshi S. Sugimura T. Shimotohno K. Proc. Natl. Acad. Sci. U. S. A. 1990; 87: 9524-9528Crossref PubMed Scopus (1087) Google Scholar, 8Choo Q.-L. Richman K.H. Han J.H. Berger K. Lee C. Dong C. Gallegos C. Coit D. Medina-Selby R. Barr P.J. Weiner A.J. Bradley D.W. Kuo G. Houghton M. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 2451-5455Crossref PubMed Scopus (1524) Google Scholar, 9Okamoto H. Okada S. Sugiyama Y. Kurai K. Iizuka H. Machida A. Miyakawa Y. Mayumi M. J. Gen. Virol. 1991; 72: 2697-6704Crossref PubMed Scopus (393) Google Scholar, 10Takamizawa A. Mori C. Fuke I. Manabe S. Murakami S. Fujita J. Onishi E. Andoh T. Yoshida I. Okayama H. J. Virol. 1991; 65: 1105-1113Crossref PubMed Scopus (0) Google Scholar). Once HCV infects cells, the positive, single-stranded RNA genome is translated into a polyprotein of 3010 to 3033 amino acids, depending upon the strain (7Kato N. Hijikata M. Ootsuyama Y. Nakagawa M. Ohkoshi S. Sugimura T. Shimotohno K. Proc. Natl. Acad. Sci. U. S. A. 1990; 87: 9524-9528Crossref PubMed Scopus (1087) Google Scholar, 8Choo Q.-L. Richman K.H. Han J.H. Berger K. Lee C. Dong C. Gallegos C. Coit D. Medina-Selby R. Barr P.J. Weiner A.J. Bradley D.W. Kuo G. Houghton M. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 2451-5455Crossref PubMed Scopus (1524) Google Scholar, 9Okamoto H. Okada S. Sugiyama Y. Kurai K. Iizuka H. Machida A. Miyakawa Y. Mayumi M. J. Gen. Virol. 1991; 72: 2697-6704Crossref PubMed Scopus (393) Google Scholar, 10Takamizawa A. Mori C. Fuke I. Manabe S. Murakami S. Fujita J. Onishi E. Andoh T. Yoshida I. Okayama H. J. Virol. 1991; 65: 1105-1113Crossref PubMed Scopus (0) Google Scholar). The viral RNA is not capped, and translation occurs via an internal ribosome entry site at the 5′ end of the viral RNA (11Reynolds J.E. Kaminski A. Kettinen H.J. Grace K. Clarke B.E. Carroll A.R. Rowlands D.J. Jackson R.J. EMBO J. 1995; 14: 6010-6020Crossref PubMed Scopus (307) Google Scholar, 12Fukushi S. Kurihara C. Ishiyama N. Hoshino F.B. Oya A. Katayama K. J. Virol. 1997; 71: 1662-1666Crossref PubMed Google Scholar). The mechanism of translation of uncapped viral RNA therefore differs from that used by virtually all cellular mRNAs that are capped at their 5′ ends. The HCV polyprotein is cleaved by both host cell and viral proteases into several smaller polypeptides (7Kato N. Hijikata M. Ootsuyama Y. Nakagawa M. Ohkoshi S. Sugimura T. Shimotohno K. Proc. Natl. Acad. Sci. U. S. A. 1990; 87: 9524-9528Crossref PubMed Scopus (1087) Google Scholar, 8Choo Q.-L. Richman K.H. Han J.H. Berger K. Lee C. Dong C. Gallegos C. Coit D. Medina-Selby R. Barr P.J. Weiner A.J. Bradley D.W. Kuo G. Houghton M. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 2451-5455Crossref PubMed Scopus (1524) Google Scholar, 9Okamoto H. Okada S. Sugiyama Y. Kurai K. Iizuka H. Machida A. Miyakawa Y. Mayumi M. J. Gen. Virol. 1991; 72: 2697-6704Crossref PubMed Scopus (393) Google Scholar, 10Takamizawa A. Mori C. Fuke I. Manabe S. Murakami S. Fujita J. Onishi E. Andoh T. Yoshida I. Okayama H. J. Virol. 1991; 65: 1105-1113Crossref PubMed Scopus (0) Google Scholar, 13Selby M.J. Choo Q.-L. Berger K. Kuo G. Glazer E. Eckart M. Lee C. Chien D. Kuo C. Houghton M. J. Gen. Virol. 1993; 74: 1103-1113Crossref PubMed Scopus (200) Google Scholar). The major structural proteins are a core protein and two envelope proteins called E1 and E2. The core protein forms the nucleocapsid of the mature virion, and E1 and E2 are present in the viral envelope. A small polypeptide called P7 is also generated as a result of cleavage at the E2-NS2 junction, but its function is not clear. Four major nonstructural proteins called NS2, NS3, NS4, and NS5 are also generated, two of which, NS4 and NS5, are further processed into smaller polypeptides called NS4A, NS4B, NS5A, and NS5B. Most of the nonstructural proteins have enzymatic activities that are critical for viral replication.After cells are infected with a virus, viral proteins can interact with host cell proteins and influence cell physiology. In previous studies, HCV core protein has been shown to bind to lymphotoxin-β receptor and other tumor necrosis factor receptor family members (14Matsumoto M. Hsieh T.Y. Zhu N. VanArsdale T. Hwang S.B. Jeng K.S. Gorbalenya A.E. Lo S.Y. Ou J.H. Ware C.F. J. Virol. 1997; 71: PubMed Google Scholar, N. A. R. M. G. Ware C. J. Virol. 72: PubMed Google Scholar). A of HCV core protein also with in the M. R. Hwang S.B. Lee J. PubMed Scopus Google Scholar). We that HCV core protein to a cellular RNA in capped RNA translation. a mechanism by which HCV may inhibit mRNA translation in infected cells or a cellular protein to its core protein to the human DEAD box protein DBX. DBX the of that it can function as a RNA for capped the essential yeast DEAD box RNA findings that HCV core protein DBX from yeast and that it the translation of capped RNA in suggest that it may inhibit cellular mRNA These translation occurs as a result of HCV core protein DBX RNA or by an interaction that in DBX at a the of the endoplasmic in function of host cell mRNA translation viral RNA with to and the of the protein of the a by several Scholar). A has shown that of of HCV structural and nonstructural proteins is to mammalian cells D. Hepatology. PubMed Scopus Google it is not from of host cell translation. Because the development of a robust cell culture system to HCV has remained it extremely to the of HCV infection host cell mRNA translation. the to the that HCV core to DBX and capped RNA translation in that it can inhibit mRNA translation in infected human box RNA capped mRNA Science. 1997; PubMed Scopus Google Scholar), and of their function translation of cellular of DBX function by HCV core protein may inhibit host mRNA translation in mammalian cells they other RNA PubMed Scopus Google Scholar). In the translation of HCV which is not capped, internal ribosome entry (11Reynolds J.E. Kaminski A. Kettinen H.J. Grace K. Clarke B.E. Carroll A.R. Rowlands D.J. Jackson R.J. EMBO J. 1995; 14: 6010-6020Crossref PubMed Scopus (307) Google Scholar, 12Fukushi S. Kurihara C. Ishiyama N. Hoshino F.B. Oya A. Katayama K. J. Virol. 1997; 71: 1662-1666Crossref PubMed Google Scholar), and can by its RNA which is of the HCV protein N. T. M. 1997; PubMed Scopus Google Scholar, J.L. C. PubMed Scopus Google Scholar), and may DBX. mechanism is of that used by which translation factor H. D. D. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, D. I. N. J. PubMed Google and also has RNA with internal ribosome entry J. N. PubMed Scopus Google Scholar). In cells, as a with which has RNA binding and which is also a DEAD box RNA F. I. K. N. 1990; 10: PubMed Scopus Google Scholar). HCV and infection may both therefore cause a in the of capped mRNA in host to capped mRNA translation in infected host cells, the interaction between HCV core protein and DBX may other the of DBX to in HCV of host cells proteins into to viral has been in other the structural protein of the human virus to and A into viral which to for efficient viral J. 1993; Scopus Google Scholar, J. 359-362Crossref PubMed Scopus Google Scholar). In a of DBX into HCV by binding to core protein may viral by DBX viral RNA in viral in infected cells. of is at the present of the lack of an efficient cell culture system for core protein has also been shown to bind to lymphotoxin-β receptor and other tumor necrosis factor receptor family members (14Matsumoto M. Hsieh T.Y. Zhu N. VanArsdale T. Hwang S.B. Jeng K.S. Gorbalenya A.E. Lo S.Y. Ou J.H. Ware C.F. J. Virol. 1997; 71: PubMed Google N. A. R. M. G. Ware C. J. Virol. 72: PubMed Google as as M. R. Hwang S.B. Lee J. PubMed Scopus Google Scholar). In yeast two-hybrid not for of in bait and the cDNA library The that other proteins interact with HCV core protein that its in cells may have R. K. R. J. 1997; PubMed Scopus Google Scholar, D.W. R. T. I. Miyamura T. J. Sci. PubMed Scopus Google have also that HCV core protein from the and other The of HCV core protein cell physiology of infection to at the present of lack of a cell culture system for it that the for chronic hepatitis C are in a of N. J. PubMed Scopus Google Scholar). interactions between HCV and host cell proteins cell or viral they for of the the binding of polypeptide to a structural or nonstructural protein of HCV may with viral The of polypeptides as DBX that bind to HCV proteins therefore has for the of which may in the of with chronic hepatitis C. Hepatitis C virus (HCV) 1The abbreviations used are: HCV, hepatitis C virus; GST, glutathione S-transferase; GPD, glyceraldehyde-3-phosphate; PCR, polymerase chain reaction1The abbreviations used are: HCV, hepatitis C virus; GST, glutathione S-transferase; GPD, glyceraldehyde-3-phosphate; PCR, polymerase chain reactionwas discovered by cDNA cloning in 1989 and shown to cause chronic liver disease (1Choo Q.-L. Kuo G. Weiner A.J. Overby L.R. Bradley D.W. Houghton M. Science. 1989; 244: 359-362Crossref PubMed Scopus (6209) Google Scholar, 2Kuo G. Choo Q.-L. Alter H.J. Gitnick G.L. Redeker A.G. Purcell R.H. Miyamura T. Dienstag J.L. Alter M.J. Stevens C.E. Tegtmeier G.E. Bonino F. Colombo M. Lee W.-S. Kou C. Berger K. Shuster J.R. Overby R. Bradley D.W. Houghton M. Science. 1989; 244: 362-364Crossref PubMed Scopus (3030) Google Scholar). Approximately 4 million Americans and 150 million individuals worldwide are infected with HCV and at risk for cirrhosis and hepatocellular carcinoma (3Alter M.J. Semin. Liver Dis. 1995; 15: 5-14Crossref PubMed Scopus (484) Google Scholar, 4Mansell C.J. Locarnini S.A. Semin. Liver Dis. 1995; 15: 15-32Crossref PubMed Scopus (109) Google Scholar, 5Mamiya N. Worman H.J. Curr. Opin. Infect. Dis. 1997; 10: 3990-3997Crossref Scopus (1) Google Scholar, 6National Institutes of Health Consensus Development Panel Hepatology. 1997; 26: 1S-156SPubMed Google Scholar). Because development of a robust cell culture system for HCV infection has remained elusive (6National Institutes of Health Consensus Development Panel Hepatology. 1997; 26: 1S-156SPubMed Google Scholar), extremely little is known about HCV-host cell interactions and how they influence cell physiology or viral HCV is a positive single-stranded RNA virus and a member of theFlaviviridae family (1Choo Q.-L. Kuo G. Weiner A.J. Overby L.R. Bradley D.W. Houghton M. Science. 1989; 244: 359-362Crossref PubMed Scopus (6209) Google Scholar, 7Kato N. Hijikata M. Ootsuyama Y. Nakagawa M. Ohkoshi S. Sugimura T. Shimotohno K. Proc. Natl. Acad. Sci. U. S. A. 1990; 87: 9524-9528Crossref PubMed Scopus (1087) Google Scholar, 8Choo Q.-L. Richman K.H. Han J.H. Berger K. Lee C. Dong C. Gallegos C. Coit D. Medina-Selby R. Barr P.J. Weiner A.J. Bradley D.W. Kuo G. Houghton M. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 2451-5455Crossref PubMed Scopus (1524) Google Scholar, 9Okamoto H. Okada S. Sugiyama Y. Kurai K. Iizuka H. Machida A. Miyakawa Y. Mayumi M. J. Gen. Virol. 1991; 72: 2697-6704Crossref PubMed Scopus (393) Google Scholar, 10Takamizawa A. Mori C. Fuke I. Manabe S. Murakami S. Fujita J. Onishi E. Andoh T. Yoshida I. Okayama H. J. Virol. 1991; 65: 1105-1113Crossref PubMed Scopus (0) Google Scholar). Once HCV infects cells, the positive, single-stranded RNA genome is translated into a polyprotein of 3010 to 3033 amino acids, depending upon the strain (7Kato N. Hijikata M. Ootsuyama Y. Nakagawa M. Ohkoshi S. Sugimura T. Shimotohno K. Proc. Natl. Acad. Sci. U. S. A. 1990; 87: 9524-9528Crossref PubMed Scopus (1087) Google Scholar, 8Choo Q.-L. Richman K.H. Han J.H. Berger K. Lee C. Dong C. Gallegos C. Coit D. Medina-Selby R. Barr P.J. Weiner A.J. Bradley D.W. Kuo G. Houghton M. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 2451-5455Crossref PubMed Scopus (1524) Google Scholar, 9Okamoto H. Okada S. Sugiyama Y. Kurai K. Iizuka H. Machida A. Miyakawa Y. Mayumi M. J. Gen. Virol. 1991; 72: 2697-6704Crossref PubMed Scopus (393) Google Scholar, 10Takamizawa A. Mori C. Fuke I. Manabe S. Murakami S. Fujita J. Onishi E. Andoh T. Yoshida I. Okayama H. J. Virol. 1991; 65: 1105-1113Crossref PubMed Scopus (0) Google Scholar). The viral RNA is not capped, and translation occurs via an internal ribosome entry site at the 5′ end of the viral RNA (11Reynolds J.E. Kaminski A. Kettinen H.J. Grace K. Clarke B.E. Carroll A.R. Rowlands D.J. Jackson R.J. EMBO J. 1995; 14: 6010-6020Crossref PubMed Scopus (307) Google Scholar, 12Fukushi S. Kurihara C. Ishiyama N. Hoshino F.B. Oya A. Katayama K. J. Virol. 1997; 71: 1662-1666Crossref PubMed Google Scholar). The mechanism of translation of uncapped viral RNA therefore differs from that used by virtually all cellular mRNAs that are capped at their 5′ ends. The HCV polyprotein is cleaved by both host cell and viral proteases into several smaller polypeptides (7Kato N. Hijikata M. Ootsuyama Y. Nakagawa M. Ohkoshi S. Sugimura T. Shimotohno K. Proc. Natl. Acad. Sci. U. S. A. 1990; 87: 9524-9528Crossref PubMed Scopus (1087) Google Scholar, 8Choo Q.-L. Richman K.H. Han J.H. Berger K. Lee C. Dong C. Gallegos C. Coit D. Medina-Selby R. Barr P.J. Weiner A.J. Bradley D.W. Kuo G. Houghton M. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 2451-5455Crossref PubMed Scopus (1524) Google Scholar, 9Okamoto H. Okada S. Sugiyama Y. Kurai K. Iizuka H. Machida A. Miyakawa Y. Mayumi M. J. Gen. Virol. 1991; 72: 2697-6704Crossref PubMed Scopus (393) Google Scholar, 10Takamizawa A. Mori C. Fuke I. Manabe S. Murakami S. Fujita J. Onishi E. Andoh T. Yoshida I. Okayama H. J. Virol. 1991; 65: 1105-1113Crossref PubMed Scopus (0) Google Scholar, 13Selby M.J. Choo Q.-L. Berger K. Kuo G. Glazer E. Eckart M. Lee C. Chien D. Kuo C. Houghton M. J. Gen. Virol. 1993; 74: 1103-1113Crossref PubMed Scopus (200) Google Scholar). The major structural proteins are a core protein and two envelope proteins called E1 and E2. The core protein forms the nucleocapsid of the mature virion, and E1 and E2 are present in the viral envelope. A small polypeptide called P7 is also generated as a result of cleavage at the E2-NS2 junction, but its function is not clear. Four major nonstructural proteins called NS2, NS3, NS4, and NS5 are also generated, two of which, NS4 and NS5, are further processed into smaller polypeptides called NS4A, NS4B, NS5A, and NS5B. Most of the nonstructural proteins have enzymatic activities that are critical for viral cells are infected with a virus, viral proteins can interact with host cell proteins and influence cell physiology. In previous studies, HCV core protein has been shown to bind to lymphotoxin-β receptor and other tumor necrosis factor receptor family members (14Matsumoto M. Hsieh T.Y. Zhu N. VanArsdale T. Hwang S.B. Jeng K.S. Gorbalenya A.E. Lo S.Y. Ou J.H. Ware C.F. J. Virol. 1997; 71: PubMed Google Scholar, N. A. R. M. G. Ware C. J. Virol. 72: PubMed Google Scholar). A of HCV core protein also with in the M. R. Hwang S.B. Lee J. PubMed Scopus Google Scholar). We that HCV core protein to a cellular RNA in capped RNA translation. a mechanism by which HCV may inhibit mRNA translation in infected cells or a cellular protein to its core protein to the human DEAD box protein DBX. DBX the of that it can function as a RNA for capped the essential yeast DEAD box RNA findings that HCV core protein DBX from yeast and that it the translation of capped RNA in suggest that it may inhibit cellular mRNA These translation occurs as a result of HCV core protein DBX RNA or by an interaction that in DBX at a the of the endoplasmic in function of host cell mRNA translation viral RNA with to and the of the protein of the a by several Scholar). A has shown that of of HCV structural and nonstructural proteins is to mammalian cells D. Hepatology. PubMed Scopus Google it is not from of host cell translation. Because the development of a robust cell culture system to HCV has remained it extremely to the of HCV infection host cell mRNA translation. the to the that HCV core to DBX and capped RNA translation in that it can inhibit mRNA translation in infected human box RNA capped mRNA Science. 1997; PubMed Scopus Google Scholar), and of their function translation of cellular of DBX function by HCV core protein may inhibit host mRNA translation in mammalian cells they other RNA PubMed Scopus Google Scholar). In the translation of HCV which is not capped, internal ribosome entry (11Reynolds J.E. Kaminski A. Kettinen H.J. Grace K. Clarke B.E. Carroll A.R. Rowlands D.J. Jackson R.J. EMBO J. 1995; 14: 6010-6020Crossref PubMed Scopus (307) Google Scholar, 12Fukushi S. Kurihara C. Ishiyama N. Hoshino F.B. Oya A. Katayama K. J. Virol. 1997; 71: 1662-1666Crossref PubMed Google Scholar), and can by its RNA which is of the HCV protein N. T. M. 1997; PubMed Scopus Google Scholar, J.L. C. PubMed Scopus Google Scholar), and may DBX. mechanism is of that used by which translation factor H. D. D. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, D. I. N. J. PubMed Google and also has RNA with internal ribosome entry J. N. PubMed Scopus Google Scholar). In cells, as a with which has RNA binding and which is also a DEAD box RNA F. I. K. N. 1990; 10: PubMed Scopus Google Scholar). HCV and infection may both therefore cause a in the of capped mRNA in host to capped mRNA translation in infected host cells, the interaction between HCV core protein and DBX may other the of DBX to in HCV of host cells proteins into to viral has been in other the structural protein of the human virus to and A into viral which to for efficient viral J. 1993; Scopus Google Scholar, J. 359-362Crossref PubMed Scopus Google Scholar). In a of DBX into HCV by binding to core protein may viral by DBX viral RNA in viral in infected cells. of is at the present of the lack of an efficient cell culture system for core protein has also been shown to bind to lymphotoxin-β receptor and other tumor necrosis factor receptor family members (14Matsumoto M. Hsieh T.Y. Zhu N. VanArsdale T. Hwang S.B. Jeng K.S. Gorbalenya A.E. Lo S.Y. Ou J.H. Ware C.F. J. Virol. 1997; 71: PubMed Google N. A. R. M. G. Ware C. J. Virol. 72: PubMed Google as as M. R. Hwang S.B. Lee J. PubMed Scopus Google Scholar). In yeast two-hybrid not for of in bait and the cDNA library The that other proteins interact with HCV core protein that its in cells may have R. K. R. J. 1997; PubMed Scopus Google Scholar, D.W. R. T. I. Miyamura T. J. Sci. PubMed Scopus Google have also that HCV core protein from the and other The of HCV core protein cell physiology of infection to at the present of lack of a cell culture system for it that the for chronic hepatitis C are in a of N. J. PubMed Scopus Google Scholar). interactions between HCV and host cell proteins cell or viral they for of the the binding of polypeptide to a structural or nonstructural protein of HCV may with viral The of polypeptides as DBX that bind to HCV proteins therefore has for the of which may in the of with chronic hepatitis C. HCV core protein to the human DEAD box protein DBX. DBX the of that it can function as a RNA for capped the essential yeast DEAD box RNA findings that HCV core protein DBX from yeast and that it the translation of capped RNA in suggest that it may inhibit cellular mRNA These translation occurs as a result of HCV core protein DBX RNA or by an interaction that in DBX at a the of the endoplasmic in function of host cell mRNA translation viral RNA with to and the of the protein of the a by several Scholar). A has shown that of of HCV structural and nonstructural proteins is to mammalian cells D. Hepatology. PubMed Scopus Google it is not from of host cell translation. Because the development of a robust cell culture system to HCV has remained it extremely to the of HCV infection host cell mRNA translation. the to the that HCV core to DBX and capped RNA translation in that it can inhibit mRNA translation in infected human cells. DEAD box RNA capped mRNA Science. 1997; PubMed Scopus Google Scholar), and of their function translation of cellular of DBX function by HCV core protein may inhibit host mRNA translation in mammalian cells they other RNA PubMed Scopus Google Scholar). In the translation of HCV which is not capped, internal ribosome entry (11Reynolds J.E. Kaminski A. Kettinen H.J. Grace K. Clarke B.E. Carroll A.R. Rowlands D.J. Jackson R.J. EMBO J. 1995; 14: 6010-6020Crossref PubMed Scopus (307) Google Scholar, 12Fukushi S. Kurihara C. Ishiyama N. Hoshino F.B. Oya A. Katayama K. J. Virol. 1997; 71: 1662-1666Crossref PubMed Google Scholar), and can by its RNA which is of the HCV protein N. T. M. 1997; PubMed Scopus Google Scholar, J.L. C. PubMed Scopus Google Scholar), and may DBX. mechanism is of that used by which translation factor H. D. D. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, D. I. N. J. PubMed Google and also has RNA with internal ribosome entry J. N. PubMed Scopus Google Scholar). In cells, as a with which has RNA binding and which is also a DEAD box RNA F. I. K. N. 1990; 10: PubMed Scopus Google Scholar). HCV and infection may both therefore cause a in the of capped mRNA in host cells. In to capped mRNA translation in infected host cells, the interaction between HCV core protein and DBX may other the of DBX to in HCV of host cells proteins into to viral has been in other the structural protein of the human virus to and A into viral which to for efficient viral J. 1993; Scopus Google Scholar, J. 359-362Crossref PubMed Scopus Google Scholar). In a of DBX into HCV by binding to core protein may viral by DBX viral RNA in viral in infected cells. of is at the present of the lack of an efficient cell culture system for HCV core protein has also been shown to bind to lymphotoxin-β receptor and other tumor necrosis factor receptor family members (14Matsumoto M. Hsieh T.Y. Zhu N. VanArsdale T. Hwang S.B. Jeng K.S. Gorbalenya A.E. Lo S.Y. Ou J.H. Ware C.F. J. Virol. 1997; 71: PubMed Google N. A. R. M. G. Ware C. J. Virol. 72: PubMed Google as as M. R. Hwang S.B. Lee J. PubMed Scopus Google Scholar). In yeast two-hybrid not for of in bait and the cDNA library The that other proteins interact with HCV core protein that its in cells may have R. K. R. J. 1997; PubMed Scopus Google Scholar, D.W. R. T. I. Miyamura T. J. Sci. PubMed Scopus Google have also that HCV core protein from the and other The of HCV core protein cell physiology of infection to at the present of lack of a cell culture system for it that the for chronic hepatitis C are in a of N. J. PubMed Scopus Google Scholar). interactions between HCV and host cell proteins cell or viral they for of the the binding of polypeptide to a structural or nonstructural protein of HCV may with viral The of polypeptides as DBX that bind to HCV proteins therefore has for the of which may in the of with chronic hepatitis C. We for and S. for M. Houghton for and J. and T. of for the