C Proteins: Controllers of Orderly Paramyxovirus Replication and of the Innate Immune Response

Oliver Siering, Roberto Cattaneo, Christian K. Pfaller

Research output: Contribution to journalReview articlepeer-review


Particles of many paramyxoviruses include small amounts of proteins with a molecular weight of about 20 kDa. These proteins, termed “C”, are basic, have low amino acid homology and some secondary structure conservation. C proteins are encoded in alternative reading frames of the phosphoprotein gene. Some viruses express nested sets of C proteins that exert their functions in different locations: In the nucleus, they interfere with cellular transcription factors that elicit innate immune responses; in the cytoplasm, they associate with viral ribonucleocapsids and control poly-merase processivity and orderly replication, thereby minimizing the activation of innate immunity. In addition, certain C proteins can directly bind to, and interfere with the function of, several cyto-plasmic proteins required for interferon induction, interferon signaling and inflammation. Some C proteins are also required for efficient virus particle assembly and budding. C-deficient viruses can be grown in certain transformed cell lines but are not pathogenic in natural hosts. C proteins affect the same host functions as other phosphoprotein gene-encoded proteins named V but use different strategies for this purpose. Multiple independent systems to counteract host defenses may ensure efficient immune evasion and facilitate virus adaptation to new hosts and tissue environments.

Original languageEnglish (US)
Article number137
Issue number1
StatePublished - Jan 2022


  • Budding
  • Defective-interfering RNA
  • Immune evasion
  • Inflammasome
  • Nucleocapsid
  • Orthoparamyxovirinae
  • Paramyxoviridae
  • Processivity
  • Replication

ASJC Scopus subject areas

  • Infectious Diseases
  • Virology


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