       Document 1132
 DOCN  M9591132
 TI    Functional mRNA can be generated by RNA polymerase III.
 DT    9509
 AU    Gunnery S; Mathews MB; Cold Spring Harbor Laboratory, New York 11724,
       USA.
 SO    Mol Cell Biol. 1995 Jul;15(7):3597-607. Unique Identifier : AIDSLINE
       MED/95311957
 AB    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.
 DE    Base Sequence  Chimeric Proteins/BIOSYNTHESIS  Chloramphenicol
       Acetyltransferase/BIOSYNTHESIS/GENETICS  Gene Products,
       tat/BIOSYNTHESIS/GENETICS  Genes, Reporter  Hela Cells  Human
       HIV-1/GENETICS  Molecular Sequence Data  Polyribosomes/METABOLISM  RNA
       Caps/ANALYSIS  RNA Polymerase III/*METABOLISM  RNA,
       Messenger/ANALYSIS/*METABOLISM  RNA, Small Nuclear/GENETICS  Support,
       Non-U.S. Gov't  Support, U.S. Gov't, P.H.S.  *Transcription, Genetic
       *Translation, Genetic  JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).

