title: Nonstructural protein 5A (NS5A) and human replication protein A increase the processivity of hepatitis C virus NS5B polymerase activity in vitro.
abstract: The precise role(s) and topological organization of different factors in the hepatitis C virus (HCV) RNA replication complex are not well understood. In order to elucidate the role of viral and host proteins in HCV replication, we have developed a novel in vitro replication system that utilizes a rolling-circle RNA template. Under close-to-physiological salt conditions, HCV NS5BΔ21, an RNA-dependent RNA polymerase, has poor affinity for the RNA template. Human replication protein A (RPA) and HCV NS5A recruit NS5BΔ21 to the template. Subsequently, NS3 is recruited to the replication complex by NS5BΔ21, resulting in RNA synthesis stimulation by helicase. Both RPA and NS5A(S25-C447), but not NS5A(S25-K215), enabled the NS5BΔ21-NS3 helicase complex to be stably associated with the template and synthesize RNA product in a highly processive manner in vitro. This new in vitro HCV replication system is a useful tool that may facilitate the study of other replication factors and aid in the discovery of novel inhibitors of HCV replication.
  
  
  OBJECTIVE
  The molecular mechanism of hepatitis C virus (HCV) replication is not fully understood, but viral and host proteins collaborate in this process. Using a rolling-circle RNA template, we have reconstituted an in vitro HCV replication system that allows us to interrogate the role of viral and host proteins in HCV replication and delineate the molecular interactions. We showed that HCV NS5A(S25-C447) and cellular replication protein A (RPA) functionally cooperate as a processivity factor to stimulate HCV replication by HCV NS5BΔ21 polymerase and NS3 helicase. This system paves the way to test other proteins and may be used as an assay for discovery of HCV inhibitors.
authors.affiliation: Infectious Diseases Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA nagraj_mani@yahoo.com.
authors.forename: Nagraj
authors.initials: N
authors.lastname: Mani
authors.affiliation: Infectious Diseases Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Yuzhakov
authors.affiliation: Infectious Diseases Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA.
authors.forename: Olga
authors.initials: O
authors.lastname: Yuzhakov
authors.affiliation: Protein Sciences Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA.
authors.forename: Joyce T
authors.initials: JT
authors.lastname: Coll
authors.affiliation: Protein Sciences Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA.
authors.forename: Jim
authors.initials: J
authors.lastname: Black
authors.affiliation: Protein Sciences Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA.
authors.forename: Kumkum
authors.initials: K
authors.lastname: Saxena
authors.affiliation: Protein Sciences Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Fulghum
authors.affiliation: Protein Sciences Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA.
authors.forename: Judith A
authors.initials: JA
authors.lastname: Lippke
authors.affiliation: Computational Sciences Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA.
authors.forename: B Govinda
authors.initials: BG
authors.lastname: Rao
authors.affiliation: Infectious Diseases Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA.
authors.forename: Rene
authors.initials: R
authors.lastname: Rijnbrand
authors.affiliation: Infectious Diseases Department, Vertex Pharmaceuticals Incorporated, Boston, Massachusetts, USA.
authors.forename: Ann D
authors.initials: AD
authors.lastname: Kwong
mesh_terms: D016174:Hepacivirus / Q000201:enzymology* / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D012367:RNA, Viral / Q000378:metabolism; D051716:Replication Protein A / Q000378:metabolism*; D017384:Sequence Deletion; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication; D012324:RNA-Dependent RNA Polymerase
chemical_list: D050505:Mutant Proteins; D012367:RNA, Viral; D051716:Replication Protein A; D017361:Viral Nonstructural Proteins; C497167:RPA1 protein, human; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase