VPg (viral protein genome-linked) is a protein that is covalently attached to the 5′ end of positive strand viral RNA and acts as a primer during RNA synthesis in a variety of virus families including Picornaviridae, Potyviridae, Astroviridae and Caliciviridae. There are some studies showing that a possible VPg protein is also present in astroviridae, however, experimental evidence for this has not yet been provided and requires further study. [1] The primer activity of VPg occurs when the protein becomes uridylated, providing a free hydroxyl that can be extended by the virally encoded RNA-dependent RNA polymerase. For some virus families, VPg also has a role in translation initiation by acting like a 5' mRNA cap.
VPg was first described in initial investigations of poliovirus RNA as a protein covalently attached to the 5' end of the genome.[2][3] and later seen in caliciviruses.[4]
- ^ Goodfellow I (November 2011). "The genome-linked protein VPg of vertebrate viruses —a multifaceted protein". Curr Opin Virol. 1 (5): 355–362. doi:10.1016/j.coviro.2011.09.003. PMC 3541522. PMID 22440837.
- ^ Flanegan JB, Petterson RF, Ambros V, Hewlett MJ, Baltimore D. Covalent linkage of a protein to a defined nucleotide sequence at the 5′-terminus of virion and replicative intermediate rnas of poliovirus. Proc Natl Acad Sci U SA. 1977;74:961–965.
- ^ Lee YF, Nomoto A, Detjen BM, Wimmer E. The genome-linked protein of picornaviruses i. A protein covalently linked to poliovirus genome rna. Proc Natl Acad Sci U S A. 1977;74:59–63.
- ^ Schaffer FL, Ehresmann DW, Fretz MK, Soergel MI. A protein, vpg, covalently linked to 36s calicivirus rna. J Gen Virol. 1980;47(1):215–220.