       Document 0254
 DOCN  M9620254
 TI    The high stability of the triple helices formed between short purine
       oligonucleotides and SIV/HIV-2 vpx genes is determined by the targeted
       DNA structure.
 DT    9602
 AU    Svinarchuk F; Monnot M; Merle A; Malvy C; Fermandjian S; Laboratoire de
       Biochimie-Enzymologie, CNRS URA 147, Institut; Gustave Roussy,
       Villejuif, France.
 SO    Nucleic Acids Res. 1995 Oct 11;23(19):3831-6. Unique Identifier :
       AIDSLINE MED/96038836
 AB    In our previous works we have shown that the oligonucleotides
       5'-GGGGAGGGGGAGG-3' and 5'-GGAGGGGGAGGGG-3' give very stable and
       specific triplexes with their target double stranded DNAs [Svinarchuk,
       F., Bertrand, J.-R. and Malvy, C. (1994) Nucleic Acids Res., 22,
       3742-3747; Svinarchuk, F., Paoletti, J. and Malvy, C. (1995) J. Biol.
       Chem., 270, 14 068-14,071]. The target for the invariable part of these
       oligonucleotides, 5'-GGAGGGGGAGG-3', is found in a highly conserved 20
       bp long purine/pyrimidine tract of the vpx gene of the SIV and HIV-2
       viruses and could be a target for oligonucleotide directed antivirus
       therapy. Here were report on the ability of four purine oligonucleotides
       with different lengths (11-, 14-, 17- and 20-mer) to form triplexes with
       the purine/pyrimidine stretch of the vpx gene. Triplex formation was
       tested by joint dimethyl sulfate (DMS) footprint, gel-retardation assay,
       circular dichroism (CD) and UV-melting studies. Dimethyl sulfate
       footprint studies revealed the antiparallel orientation of the third
       strand to the purine strand of the Watson-Crick duplex. However, the
       protection of the guanines at the ends of the target sequence decreased
       as the length of the third strand oligonucleotide increased. Melting
       temperature studies provided profiles with only one transition for all
       of the triplexes. The melting temperatures of the triplexes were found
       to be the same as for the targeted duplex in the case of the 11- and
       14-mer third strands while for the 17- and 20-mer third strands the
       melting temperature of the triplexes were correspondingly 4 and 8
       degrees C higher than for the duplex. Heating and cooling melting curves
       were reversible for all of the tested triplexes except one with the
       20-mer third strand oligonucleotide. Circular dichroism spectra showed
       the ability of the target DNA to adopt an A-like DNA conformation. Upon
       triplex formation the A-DNA form becomes even more pronounced. This
       effect depends on the length of the third strand oligonucleotide: the CD
       spectrum shows a 'classical' A-DNA shape with the 20-mer. This is not
       observed with the purine/pyrimidine stretch of the HIV-1 DNA which keeps
       a B-like spectrum even after triplex formation. We suggest, that an
       A-like duplex DNA is required for the formation of a stable DNA
       purine(purine-pyrimidine) triplex.
 DE    Base Sequence  Circular Dichroism  Drug Stability  DNA Footprinting
       DNA, Viral/*CHEMISTRY  Genes, Viral  HIV-2/*GENETICS
       Magnesium/PHARMACOLOGY  Molecular Sequence Data  *Nucleic Acid
       Conformation  Purine Nucleotides/*CHEMISTRY  Support, Non-U.S. Gov't
       SIV/*GENETICS  Viral Regulatory Proteins/*GENETICS  JOURNAL ARTICLE

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

