       Document 0428
 DOCN  M9490428
 TI    A molecular rheostat. Co-operative rev binding to stem I of the
       rev-response element modulates human immunodeficiency virus type-1 late
       gene expression.
 DT    9411
 AU    Mann DA; Mikaelian I; Zemmel RW; Green SM; Lowe AD; Kimura T; Singh M;
       Butler PJ; Gait MJ; Karn J; MRC Laboratory of Molecular Biology,
       Cambridge, U.K.
 SO    J Mol Biol. 1994 Aug 12;241(2):193-207. Unique Identifier : AIDSLINE
       MED/94334977
 AB    The complete biologically active human immunodeficiency virus type-1
       (HIV-1) rev-response element (RRE) RNA is 351 nucleotides (nt) in
       length, and includes an extra 58 nt on the 5' end and 59 nt on the 3'
       end beyond the sites proposed in the original models for the RRE
       secondary structure. The extra sequences are able to form a duplex
       structure which extends Stem I. The presence of an elongated Stem I
       structure in the RRE RNA was confirmed by nuclease mapping experiments.
       Nuclease protection experiments have shown that rev binds to restricted
       regions of the RRE, including the high affinity site located at the base
       of Stem IIb and along the length of the Stem I region. The three large
       stem-loop structures which protrude from Stem I and Stem IIb (Stems IIc,
       III+IV and V) remain accessible to nucleases even in the presence of a
       large excess of protein. Gel-retardation experiments show that the
       truncations of Stem I reduced the total number of rev molecules that can
       bind co-operatively and with high affinity to the RRE RNA. To test
       whether the elongated Stem I structure is required for maximal rev
       activity, a series of truncations which progressively reduced the length
       of Stem I was introduced into an HIV-1 derived reporter plasmid. In the
       presence of rev and a functional RRE, there is an increase in the levels
       of gag and env mRNA in the cytoplasm and a decrease in levels of tat and
       rev mRNAs. Each of the truncations in Stem I reduced the rev responses,
       with the longest truncations producing the greatest losses of activity.
       The data suggest that the RRE acts as a molecular rheostat designed to
       detect rev levels during the early stages of the HIV growth cycle.
 DE    Base Sequence  Binding Sites  Electrophoresis, Polyacrylamide Gel  Gene
       Expression Regulation, Viral/*GENETICS  Gene Products, rev/*METABOLISM
       Genes, env/*GENETICS  Genes, gag/GENETICS  Genes, tat/GENETICS  Hela
       Cells  Human  HIV-1/*GENETICS  Molecular Sequence Data  Mutagenesis
       Nucleic Acid Conformation  Polymerase Chain Reaction  RNA,
       Viral/CHEMISTRY/*GENETICS/METABOLISM  Support, Non-U.S. Gov't
       Transfection  JOURNAL ARTICLE

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

