Regulation of mRNA 1 expression by the 5'-untranslated region (5'-UTR) of the coronavirus infectious bronchitis virus (IBV).
In this report, we show that expression of the coronavirus IBV mRNA1 is regulated by its 5'-UTR. Evidence presented demonstrates that the IBV sequence from nucleotide 1 to 1904 directs very inefficient synthesis of a product of approximately 43 kDa. Deletion of either the first 362 bp or the whole part of the 5'-UTR, however, dramatically increased the expression of the 43 kDa protein species. The mechanisms involved were investigated by two different approaches. Firstly, translation of the same construct in the presence of [3H]-leucine ruled out the possibility that initiation of small reading frames from non-AUG codons located in the 5'-UTR may compete with the authentic AUG initiation codon, and therefore inhibit the expression of ORF 1a. Secondly, expression and deletion analyses of a dicistronic construct showed that translation of the 43 kDa protein was initiated by ribosome internal entry mechanism. These studies suggest that a 'weak' ribosome internal entry signal is located in the 5'-UTR and is involved in the regulation of mRNA1 expression.
Institute of Molecular Agrobiology, National University of Singapore.
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Lim
D020121:5' Untranslated Regions; D000818:Animals; D018387:Codon, Initiator; D015967:Gene Expression Regulation, Viral; D001351:Infectious bronchitis virus / Q000235:genetics*; D014176:Protein Biosynthesis; D012315:RNA Caps; D012333:RNA, Messenger; D012367:RNA, Viral; D016364:Reading Frames; D014764:Viral Proteins / Q000235:genetics
D020121:5' Untranslated Regions; D018387:Codon, Initiator; D012315:RNA Caps; D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins; C087637:gene 1 protein, Coronavirus