Polo-like kinase 1 is involved in hepatitis C virus replication by hyperphosphorylating NS5A.
Hepatitis C virus (HCV) replication involves many viral and host factors. Here, we employed a lentivirus-based RNA interference (RNAi) screening approach to search for possible cellular factors. By using a kinase-phosphatase RNAi library and an HCV replicon reporter system, we identified a serine-threonine kinase, Polo-like kinase 1 (Plk1), as a potential host factor regulating HCV replication. Knockdown of Plk1 reduced both HCV RNA replication and nonstructural (NS) protein production in both HCV replicon cells and HCV-infected cells while it did not significantly affect host cellular growth or cell cycle. Overexpression of Plk1 in the knockdown cells rescued HCV replication. Interestingly, the ratio between the hyperphosphorylated form (p58) and the basal phosphorylated form (p56) of NS5A was lower in the Plk1 knockdown cells and Plk1 kinase inhibitor-treated cells than in the control groups. Further studies showed that Plk1 could be immunoprecipitated together with NS5A. Both proteins partially colocalized in the perinuclear region. Furthermore, Plk1 could phosphorylate NS5A to both the p58 and p56 forms in an in vitro assay system; the phosphorylation efficiency was comparable to that of the reported casein kinase. Taken together, this study shows that Plk1 is an NS5A phosphokinase and thereby indirectly regulates HCV RNA replication. Because of the differential effects of Plk1 on HCV replication and host cell growth, Plk1 could potentially serve as a target for anti-HCV therapy.
Institute of Microbiology and Immunology, National Yang-Ming University, Taipei 112, Taiwan.
Yung-Chia
YC
Chen
Wen-Chi
WC
Su
Jing-Ying
JY
Huang
Ti-Chun
TC
Chao
King-Song
KS
Jeng
Keigo
K
Machida
Michael M C
MM
Lai
D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D055785:Gene Knockdown Techniques / Q000379:methods; D005822:Genetic Vectors; D016174:Hepacivirus / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D047468:Immunoprecipitation; D016086:Lentivirus / Q000235:genetics; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012367:RNA, Viral / Q000096:biosynthesis; D017361:Viral Nonstructural Proteins / Q000378:metabolism*; D014764:Viral Proteins / Q000096:biosynthesis; D014779:Virus Replication; D000097869:Polo-Like Kinase 1; D012324:RNA-Dependent RNA Polymerase
D018797:Cell Cycle Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D012367:RNA, Viral; D017361:Viral Nonstructural Proteins; D014764:Viral Proteins; D000097869:Polo-Like Kinase 1; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase