Translational activation in coliphage Qbeta: on a polycistronic messenger RNA, repression of one gene can activate translation of another.
We present evidence for translational activation of the Qbeta coliphage maturation cistron, mediated by the presence of Qbeta replicase. This activation does not require RNA replication, translation of a second gene, or any direct protein-RNA binding at the maturation gene initiation site. Our data support a model in which the Qbeta maturation gene remains translationally "off" by two means: (1) the thermodynamic stability of an RNA structure that greatly discourages, but does not eliminate, ribosome access at the maturation start site; and (2) the presence of the stronger, proximal coat gene ribosome binding site. Moreover, maturation gene expression is switched "on" when ribosome entry at the coat initiation site, present on the same polycistronic RNA molecule, is repressed by Qbeta replicase, thereby allowing ribosomes to compete for the weaker, upstream maturation start site.
Priano
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Health Science Center at Brooklyn, State University of New York, , 450 Clarkson Ave., Brooklyn, NY 11203, USA.
Arora
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Jayant
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Mills
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D017908:Allolevivirus / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites; D002213:Capsid / Q000235:genetics; D015870:Gene Expression; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral; D014176:Protein Biosynthesis; D011777:Q beta Replicase / Q000378:metabolism; D012333:RNA, Messenger; D012367:RNA, Viral; D012270:Ribosomes / Q000378:metabolism; D015854:Up-Regulation; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics*; D015678:Viral Structural Proteins / Q000235:genetics
D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins; D015678:Viral Structural Proteins; D011777:Q beta Replicase