Functional mRNA can be generated by RNA polymerase III

Gunnery, S., Mathews, M. B. (July 1995) Functional mRNA can be generated by RNA polymerase III. Mol Cell Biol, 15 (7). pp. 3597-607. ISSN 0270-7306 (Print)

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Eukaryotic cellular mRNA is believed to be synthesized exclusively by RNA polymerase II (pol II), whereas pol I produces long rRNAs and pol III produces 5S rRNA, tRNA, and other small RNAs. To determine whether this functional differentiation is obligatory, we examined the translational potential of an artificial pol III transcript. The coding region of the human immunodeficiency virus type 1 tat gene was placed under the control of a strong pol III promoter from the adenovirus type 2 VA RNAI gene. The resultant chimera, pVA-Tat, was transcribed accurately in vivo and in vitro and gave rise to Tat protein, which transactivated a human immunodeficiency virus-driven chloramphenicol acetyltransferase reporter construct in transfected HeLa cells. pol III-specific mutations down-regulated VA-Tat RNA production in vivo and in vitro and dramatically reduced chloramphenicol acetyltransferase transactivation. As expected for a pol III transcript, VA-Tat RNA was not detectably capped at its 5' end or polyadenylated at its 3' end, but, like mRNA, it was associated with polysomes in a salt-stable manner. Mutational analysis of a short open reading frame upstream of the Tat-coding sequence implicates scanning in the initiation of VA-Tat RNA translation despite the absence of a cap. In comparison with tat mRNA generated by pol II, VA-Tat RNA was present on smaller polysomes and was apparently translated less efficiently, which is consistent with a relatively low initiation rate. Evidently, human cells are capable of utilizing pol III transcripts as functional mRNAs, and neither a cap nor a poly(A) tail is essential for translation, although they may be stimulatory. These findings raise the possibility that some cellular mRNAs are made by pol I or pol III.

Item Type: Paper
Uncontrolled Keywords: Base Sequence Chloramphenicol O-Acetyltransferase/biosynthesis/genetics Gene Products, tat/biosynthesis/genetics Genes, Reporter HIV-1/genetics Hela Cells Humans Molecular Sequence Data Polyribosomes/metabolism Protein Biosynthesis RNA Caps/analysis RNA Polymerase III/ metabolism RNA, Messenger/analysis/ metabolism RNA, Small Nuclear/genetics Recombinant Fusion Proteins/biosynthesis Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. Transcription, Genetic
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > transcription
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > enzymes > RNA polymerase
organism description > animal > mammal > primates > hominids > human
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > mRNA
CSHL Authors:
Communities: CSHL labs
Depositing User: Jessica Koos
Date: July 1995
Date Deposited: 08 Aug 2014 20:08
Last Modified: 08 Aug 2014 20:08
PMCID: PMC230597
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