       Document 0662
 DOCN  M9630662
 TI    Tat functions to stimulate the elongation properties of transcription
       complexes paused by the duplicated TAR RNA element of human
       immunodeficiency virus 2.
 DT    9603
 AU    Garcia-Martinez LF; Mavankal G; Peters P; Wu-Baer F; Gaynor RB;
       Department of Medicine, University of Texas Southwestern Medical; Center
       at Dallas 75235, USA.
 SO    J Mol Biol. 1995 Dec 1;254(3):350-63. Unique Identifier : AIDSLINE
       MED/96095795
 AB    In this study we have defined the in vitro requirements for
       transcriptional regulation of the HIV-2 LTR in response to the HIV-1 and
       HIV-2 Tat proteins and addressed potential mechanisms of Tat function.
       HIV-2 contains a duplicated TAR RNA stem-loop structure in contrast to
       the single stem-loop structure found in HIV-1 TAR RNA. We demonstrated
       that the HIV-2 proximal TAR RNA stem-loop structure was more important
       for in vitro transcriptional activation by the HIV-1 and HIV-2 Tat
       proteins than the distal TAR RNA stem-loop though this downstream TAR
       element itself was able to confer Tat-responsiveness. The role of the
       two HIV-2 TAR RNA stem-loop bulge sequences was less critical than the
       loop sequences for in vitro transcriptional activation by Tat. In
       addition, we demonstrated that replacing the HIV-2 TATA element with
       that of HIV-1 markedly reduced the overall level of Tat activation. The
       role of the Tat-1 and Tat-2 proteins on the synthesis of HIV-1 and HIV-2
       promoter proximal and promoter distal transcripts was then investigated.
       In contrast to the HIV-1 promoter, the HIV-2 promoter generated abundant
       levels of short transcripts in vitro transcription assays likely due to
       the structure of its duplicated TAR element. Both Tat-1 and Tat-2
       increased the level of transcripts extending to the end of the HIV-1 and
       HIV-2 TAR elements as well as the level of transcripts extending more
       than 500 nucleotides from the transcription initiation site. However,
       the synthesis of transcripts within 30 nucleotides of the HIV-2 LTR
       transcription initiation site was unchanged in either the presence or
       absence of Tat while the level of transcripts extending increasing
       distances from the HIV-2 LTR transcription initiation site were
       progressively stimulated in the presence of Tat. Though the HIV-1 Tat
       protein was a stronger inducer of HIV-1 LTR transcription than the HIV-2
       Tat protein, we did not detect differences in the binding of these
       proteins to the HIV-1 and HIV-2 TAR RNAs. This suggested that
       differences in their transactivation properties may be due to
       alterations in their association with RNA polymerase II or associated
       elongation factors. (ABSTRACT TRUNCATED AT 250 WORDS)
 DE    Base Sequence  Comparative Study  *Gene Expression Regulation, Viral
       Gene Products, tat/*METABOLISM  Hela Cells  Human  HIV Long Terminal
       Repeat/*GENETICS  HIV-1/GENETICS  HIV-2/*GENETICS  Molecular Sequence
       Data  Mutation  Nucleic Acid Conformation  Promoter Regions (Genetics)
       Protein Binding  RNA Precursors/BIOSYNTHESIS  RNA-Binding
       Proteins/METABOLISM  RNA, Viral/*GENETICS  Species Specificity  Support,
       Non-U.S. Gov't  Support, U.S. Gov't, Non-P.H.S.  Support, U.S. Gov't,
       P.H.S.  *Transcription, Genetic  JOURNAL ARTICLE

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

