Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Avian infectious bronchitis virus (IBV) defective RNAs (D-RNAs) have been used for the expression of heterologous genes in a helper-virus-dependent expression system. The heterologous genes were expressed under the control of an IBV transcription-associated sequence (TAS) derived from gene 5 of IBV Beaudette. However, coronavirus D-RNA expression vectors display an inherent instability following serial passage with helper virus, resulting in the eventual loss of the heterologous genes. The use of the picornavirus encephalomyocarditis virus (EMCV) internal ribosome entry site (IRES) sequence to initiate gene translation was investigated as an alternative method to the coronavirus-mediated TAS-controlled heterologous gene expression system. IBV D-RNAs containing the chloramphenicol acetyltransferase (CAT) reporter gene, under EMCV IRES control, were assessed for IRES-mediated CAT protein translation. CAT protein was detected from T7-derived IBV D-RNA transcripts in a cell-free protein synthesis system and in situ in avian chick kidney (CK) cells following T7-derived D-RNA synthesis from a recombinant fowlpox virus expressing the bacteriophage T7 DNA-dependent RNA polymerase. However, CAT protein was not detected in CK cells from IRES-containing IBV D-RNAs, in which the IRES-CAT construct was inserted at two different positions within the D-RNA, in the presence of helper IBV. Northern blot analysis demonstrated that the IRES-containing D-RNAs were not rescued on serial passage with helper virus, indicating that the EMCV IRES sequence had a detrimental effect on IBV D-RNA rescue.
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PMID:Presence of an encephalomyocarditis virus internal ribosome entry site sequence in avian infectious bronchitis virus defective RNAs abolishes rescue by helper virus. 1499 Jun 91

Avian infectious bronchitis virus (IBV) is responsible of significant economic losses for poultry industry around the world, through evolution of its pathogenicity, inadequacy of vaccines, and virus evasion. Such evasion is related to the unstable nature of its RNA, in particular the S glycoprotein encoding gene, which raises great challenges with regard to the control of the disease, along with the lack of proof reading mechanisms of the RNA polymerase. The emergence of new variants might be a reason for the endemic outbreaks that are being reported in Tunisia, in addition to poor vaccination techniques and ineffective prophylactic programs. In the present study, partial nucleotide sequences of the S1 glycoprotein gene and the 3'-untranslated region (UTR) of 2 Tunisian isolates, TN1011/16 and TN1012/16, identified in 2016, were determined. Specific mutations were found in S1 gene as well as in 3'UTR region. Phylogenetic analysis of the S1 nucleotide sequences showed that both isolates are closely related to the Algerian strains, and formed a common cluster within the genotype I. In addition, these isolates were non-recombinant ones, confirming that they are unique variants. Based on their S1 gene sequences, TN1011/16 and TN1012/16 strains were distant from the H120 vaccine strain, commercially used in Tunisia along with the variant vaccine 793B type (4/91). A comparison between nucleotide sequences of their 3'UTR region and S1 gene showed a difference in IBV classification. The obtained results have confirmed that the IBVsequence continues to drift and brings valuable information in relation with its evolution, vaccine development and better control of the disease.
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PMID:Molecular characterization of a unique variant of avian infectious bronchitis virus in Tunisia. 3126 9