title: Analysis of helicase domain mutations in the hepatitis E virus derived from patients with fulminant hepatic failure: effects on enzymatic activities and virus replication.
abstract: Fulminant hepatic failure (FHF) is the severe form of hepatitis E virus infection. Virus sequence analyses from severe cases have shown presence of unique and highly conserved mutations in the helicase domain of genotype 1, 3 and 4 viruses. We evaluated role of two amino acid replacements (L1110F) and (V1120I); found to be frequent in genotype 1 FHF-E viruses from India. Three mutant helicase proteins (two with single point mutations and one with dual mutations) were expressed in Escherichia coli and evaluated for their ATPase and RNA unwinding activities. Both L1110F and V1120I helicase mutants showed marginal decrease in ATPase activity, while L1110F/V1120I dual mutant showed normal ATPase activity. All three mutants proteins showed RNA unwinding activities comparable to wild type protein. Corresponding mutations were made in the helicase domain of HEV RLuc replicon and replication efficiencies were tested in the S10-3 (Huh 7) cells. The mutant replicon V1120I showed lower replication as compared to L1110F and L1110F/V1120I mutants. However, all three replicon mutants showed lower replication efficiencies as compared to the wild type replicon. Walker A and Walker B motif mutant HEV replicons were unable to replicate indicating essential role of the virus encoded helicase domain during HEV replication. FHF-E associated helicase mutations resulted in only marginal decrease in the virus replication suggesting alternate function/s of the helicase protein. Mutations in the helicase domain of FHF-E viruses may be responsible for changing virus or host-virus protein-protein interactions, causing alterations in the host responses, eventually leading to more severe disease manifestations.
authors.affiliation: Hepatitis Division, National Institute of Virology, Microbial Containment Complex, Sus Road, Pashan, Pune 411021, India.
authors.forename: Pradip
authors.initials: P
authors.lastname: Devhare
authors.affiliation: Hepatitis Division, National Institute of Virology, Microbial Containment Complex, Sus Road, Pashan, Pune 411021, India.
authors.forename: Kavyanjali
authors.initials: K
authors.lastname: Sharma
authors.affiliation: Hepatitis Division, National Institute of Virology, Microbial Containment Complex, Sus Road, Pashan, Pune 411021, India.
authors.forename: Vaibhav
authors.initials: V
authors.lastname: Mhaindarkar
authors.affiliation: Hepatitis Division, National Institute of Virology, Microbial Containment Complex, Sus Road, Pashan, Pune 411021, India.
authors.forename: Vidya
authors.initials: V
authors.lastname: Arankalle
authors.affiliation: Hepatitis Division, National Institute of Virology, Microbial Containment Complex, Sus Road, Pashan, Pune 411021, India. Electronic address: lolekavita37@yahoo.com.
authors.forename: Kavita
authors.initials: K
authors.lastname: Lole
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D002460:Cell Line; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D016752:Hepatitis E virus / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D022781:Hepatocytes / Q000821:virology; D006801:Humans; D007194:India; D017114:Liver Failure, Acute / Q000821:virology*; D020125:Mutation, Missense; D020365:RNA Helicases / Q000235:genetics* / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D000251:Adenosine Triphosphatases; D020365:RNA Helicases
keywords: Fulminant hepatic failure; Helicase; Hepatitis E virus; Mutations