Mutations in the measles virus C protein that up regulate viral RNA synthesis

Virology. 2001 Jun 20;285(1):100-9. doi: 10.1006/viro.2001.0962.

Abstract

The measles virus RNA-dependent RNA polymerase consists of two virus-encoded subunits, the phosphoprotein (P) and the large (L) protein. The P mRNA also codes for a C protein in the +1 reading frame relative to P. The activities of the measles P and C proteins from the vaccine strain, EdB, a wild-type CM strain, and an SSPE P4 strain were investigated using a CAT reporter minigenome assay. CAT is synthesized following replication and transcription of a DI-CAT minigenome supported by individual P, L, and N plasmids expressed in a mammalian expression system. As measured by CAT activity, CMP1 and P4P1 stimulate transcription and replication four- to six- and six- to eightfold, respectively, better than EdP. There are 10 and 16 amino acid changes in the P protein and three and four changes in C in CMP1 and P4P1, respectively, relative to EdP. By constructing chimeric P genes we showed that mutations throughout P4P1 were required for enhanced polymerase activity, while only mutations in the 5'-terminal portion, encompassing the C ORF, of the CMP1 gene mediated stimulation. Abrogation of C expression from the Ed and CM P genes resulted in an increase in RNA synthesis of twofold for CMP1S and four- to fivefold for EdPS. With the addition of C protein expressed from a separate plasmid that contains only the C ORF, EdC reduces viral RNA synthesis more strongly than CMC. These data suggest that EdC and CMC proteins give a differential inhibition that accounts for most of the differences in RNA synthesis by EdP and CMP1.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Carrier Proteins / genetics*
  • Cell Line
  • Chloramphenicol O-Acetyltransferase / metabolism
  • Measles Vaccine
  • Measles virus / chemistry
  • Measles virus / genetics
  • Measles virus / metabolism*
  • Mutation
  • Nucleocapsid Proteins / genetics
  • Phosphoproteins / genetics
  • RNA, Viral / biosynthesis*
  • Recombination, Genetic
  • Subacute Sclerosing Panencephalitis / virology
  • Transcription, Genetic
  • Up-Regulation

Substances

  • Carrier Proteins
  • Measles Vaccine
  • Nucleocapsid Proteins
  • Phosphoproteins
  • RNA, Viral
  • citrate-binding transport protein
  • Chloramphenicol O-Acetyltransferase