Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The dsRNA genome (5.2 kbp) of Helminthosporium victoriae 190S totivirus (Hv190SV) consists of two large overlapping open reading frames (ORFs). The 5' proximal ORF codes for the capsid protein (CP) and the 3' ORF codes for an RNA-dependent RNA polymerase. Although the capsid of Hv190SV is encoded by a single gene, it is composed of two major closely related polypeptides, either p88 and p83 or p88 and p78. Whereas p88 and p83 are phosphoproteins, p78 is nonphosphorylated. Expression of the CP ORF in insect cells generated both p78 and p88 which assembled into virus-like particles. The finding that p78, p83, and p88 share a common N-terminal amino acid sequence is consistent with the determination that N-terminal, but not C-terminal, CP deletions were incompetent for assembly. Evidence was obtained that p78 is derived from p88 via proteolytic cleavage at the C-terminus. Proteolytic processing may play a regulatory role in the virus life cycle since it leads to dephosphorylation of CP and a subsequent decrease in virion transcriptional activity.
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PMID:Expression, assembly, and proteolytic processing of Helminthosporium victoriae 190S totivirus capsid protein in insect cells. 923 54

The genome of Helminthosporium victoriae 190S totivirus (Hv190SV) consists of two large overlapping open reading frames (ORFs), encoding a capsid protein (CP) and an RNA-dependent RNA polymerase. The capsid of Hv190SV, even though encoded by a single gene, contains three closely related capsid polypeptides: p88, p83, and p78. p88 and p83 are phosphorylated, whereas p78, which is derived from p88 via proteolytic processing at the C terminus, is nonphosphorylated. In this study we expressed the CP ORF in bacteria and determined that a single product comigrating with virion p88 was generated. Evidence from in vivo phosphorylation studies indicated that the bacterially expressed p88 was unmodified, and thus autophosphorylation was ruled out. Enzymatic-dephosphorylation experiments using 32P-labeled p88 as a substrate demonstrated that the phosphorylated and nonphosphorylated forms of p88 could not be differentiated based on their mobilities in SDS gels and suggested that the two forms occur in purified virions. We also showed that the unmodified p88 is competent for assembly into virus-like particles, indicating that neither phosphorylation nor proteolytic processing of CP is required for capsid assembly. Posttranslational modification of CP, however, is proposed to play an important role in the life cycle of Hv190SV, including regulation of transcription/replication and/or packaging/release from virions of the viral (+) strand RNA transcript.
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PMID:Assembly of the Hv190S totivirus capsid is independent of posttranslational modification of the capsid protein. 983 97