       Document 0373
 DOCN  M9630373
 TI    Use of an oligoribonucleotide containing the polypurine tract sequence
       as a primer by HIV reverse transcriptase.
 DT    9603
 AU    Fuentes GM; Rodriguez-Rodriguez L; Fay PJ; Bambara RA; Department of
       Microbiology & Immunology, University of Rochester,; School of Medicine
       and Dentistry, New York 14642, USA.
 SO    J Biol Chem. 1995 Nov 24;270(47):28169-76. Unique Identifier : AIDSLINE
       MED/96081850
 AB    A primary site for initiation of plus strand DNA synthesis in human
       immunodeficiency virus (HIV) corresponds to a 19-nucleotide-long purine
       rich sequence located just upstream of the U3 region, designated the
       polypurine tract (PPT). The HIV reverse transcriptase (RT) uses its
       RNase H activity to cut the genomic RNA after minus strand DNA
       synthesis. A plus strand PPT primer is formed, extended, and then
       removed. In vitro, the HIV-RT recognizes this primer specifically, using
       it much more efficiently than other RNA primers. However, the PPT still
       primes significantly less efficiently than DNA primers. The
       19-nucleotide PPT primer is partially resistant to degradation when
       compared with other oligoribonucleotides. Prior to initiation of DNA
       synthesis, several nucleotides are removed by the RT from the 3' ends of
       some of the PPT primers. Cleavage is enhanced in the absence of dNTPs.
       We suggest that DNA synthesis suppresses primer degradation, so that
       primer extension and cleavage occur in proper sequence. As a result of
       3' end degradation, PPT elongation products contain 5'-RNA segments from
       16 to 19 nucleotides in length. These shorter segments are also
       generated from a longer transcript containing the PPT sequence,
       indicating that they are not created as a result of binding of the RT to
       the 5' end of the PPT oligoribonucleotide. Full-length and shorter
       versions of the PPT primers are cleaved from the extended DNA by RT.
       These experiments show that HIV-RT has a specificity to generate a
       primer in the region of the PPT but that the ends of the primer are not
       well defined.
 DE    Base Sequence  Binding Sites  DNA Primers/CHEMISTRY/*METABOLISM  DNA,
       Viral/BIOSYNTHESIS  Human  HIV/*ENZYMOLOGY  Kinetics  Molecular Sequence
       Data  Nucleic Acid Hybridization  Purines  RNA-Directed DNA
       Polymerase/*METABOLISM  Substrate Specificity  Support, Non-U.S. Gov't
       Support, U.S. Gov't, P.H.S.  Templates  JOURNAL ARTICLE

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

