Disease relevance of PVgp1

• Identification of the initiation site of poliovirus polyprotein synthesis [1].
• Mammalian (+)-strand RNA viruses and retroviruses have responded by reducing the number of cis-acting regulatory elements, a constraint that has led to the emergence of the polyprotein [2].
• The amino termini of capsid polypeptides VP1 and VP3 were determined by direct sequencing, and the other proteolytic cleavage sites in the polyprotein were predicted by comparison with other picornavirus proteins [3].
• This genome includes a 5' untranslated region, relatively well-conserved when compared with aphtho- and cardioviruses, followed by an open reading frame coding for a 2180-amino acid-long polyprotein [3].
• We have engineered a segment of the poliovirus genome (nucleotides 5438-6061) that encodes the 183 amino acid residues of the 3C region and 25 residues of the 3D region of the viral polyprotein into an Escherichia coli expression vector [4].

High impact information on PVgp1

• Proteolysis of the viral polyprotein into the mature proteins is assured by the viral 3C enzymes, which are cysteine proteinases [5].
• Poliovirus is a (+)-stranded picornavirus whose polyprotein, encoded by an open reading frame spanning most of the viral RNA, is processed by virus-encoded proteinases [2].
• Twelve viral polypeptides have been mapped by amino acid sequence analysis and were found to be proteolytic cleavage products of the polyprotein, cleavages occurring predominantly at Gln-Gly pairs [6].
• An open reading frame of 2,207 consecutive triplets spans over 89% of the nucleotide sequence and codes for the viral polyprotein NCVPOO [6].
• Cell-free translation of poliovirus RNA in an extract of uninfected human (HeLa) cells yielded viral proteins through proteolysis of the polyprotein [7].

Chemical compound and disease context of PVgp1

• The poliovirus polyprotein is cotranslationally linked to myristic acid at its amino-terminal glycine residue [8].
• The mechanism which limits cleavage to only 2 of the 10 Tyr-Gly dipeptides within the poliovirus polyprotein has not been characterized [9].
• In this study, we have investigated the effects on P1 polyprotein processing and subsequent assembly of processed capsid proteins caused by substitution of the glycine residue at the individual QG cleavage sites with valine (QG-->QV) [10].
• Poliovirus protease 3C is a cysteine enzyme that is essential for the processing of the viral precursor polyprotein containing structural proteins and enzymes, including the protease itself [11].
• Previously, it was shown that pyrrolidine dithiocarbamate (PDTC) inhibits proteolytic polyprotein processing and replication of human rhinovirus by transporting metal ions into cells [12].

Biological context of PVgp1

• We concluded that synthesis of the poliovirus polyprotein is initiated at nucleotide 743, the first AUG codon in the long open reading frame [1].
• This indicates that 2A is a multifunctional protein involved directly or indirectly in the activation of viral mRNA translation, in addition to its known roles in viral polyprotein processing and in inhibition of cellular protein synthesis [13].
• In addition, a short unlinked reading frame of 92 codons has been identified by sequence homology to the polyprotein initiation signal and by in vitro translation studies [14].
• Picornaviruses encode for their own proteinases, which are responsible for the proteolytic processing of the polyprotein encoded in the viral genome to produce the mature viral polypeptides [15].
• A small-plaque phenotype was observed when an AUG codon was inserted in frame or out of frame with regard to the initiation site of viral polyprotein synthesis [16].

Anatomical context of PVgp1

• Because all proteins that map at the amino terminus of the polyprotein (P1-1a, VP0, and VP4) are blocked at their amino termini and previous studies of ribosome binding have been inconclusive, direct identification of the initiation site of protein synthesis was difficult [1].
• A portion of the poliovirus polyprotein containing the 2Apro cleavage site at the P1/P2 junction was produced by translation of cDNA transcripts in rabbit reticulocyte lysates and then tested as a substrate for 2Apro-mediated cleavage [17].
• Since these defects are observed under conditions where no abnormalities in the rate of synthesis and processing of the mutant polyprotein occur, the inability to induce the cytopathic effect in infected Vero cells denotes the existence of a defect in the activity of 3A, but not the level of expression of the viral genome [18].

Associations of PVgp1 with chemical compounds

• This defect appeared to be due to the impaired initiation of viral polyprotein synthesis as evidenced by a relatively low level of accumulation of polypeptide 1a (which corresponds to an NH2-terminal region of the polyprotein) in samples programmed with RNAs from attenuated strains [19].

Analytical, diagnostic and therapeutic context of PVgp1

• Sequence analysis of trypsin-digested VP4, which has a blocked amino terminus, demonstrates that VP4 is encoded at or very near to the amino terminus of the polyprotein [20].
• A group of proteins derived from the P3 region of the polyprotein was identified by immunoprecipitation, time course, and N-formyl-[35S]methionine labeling studies to be the product of the initiation of protein synthesis at an internal site(s) located within the 3'-proximal RNA sequences [21].
• Oligonucleotide-directed site-specific mutagenesis of an infectious poliovirus type 1 (Mahoney strain) cDNA was used to change the Gln-Gly site at the 3C/3D junction of the polyprotein into Gln-Val, Gln-Ala, Gln-Ser or Gln-Pro [22].

References