Document 0817
 DOCN  M94B0817
 TI    Nucleotide insertion and primer extension at abasic template sites in
       different sequence contexts.
 DT    9412
 AU    Goodman MF; Cai H; Bloom LB; Eritja R; Department of Biological
       Sciences, University of Southern; California, Los Angeles 90089-1340.
 SO    Ann N Y Acad Sci. 1994 Jul 29;726:132-42; discussion 142-3. Unique
       Identifier : AIDSLINE MED/94379618
 AB    Efficiencies of insertion and extension at a single site-directed abasic
       lesion, X, were measured while varying 5'- and 3'-template bases
       adjacent to X. The preference for insertion was found to be A > G > T
       approximately C, with the upstream (3'-neighboring) template base
       perturbing insertion efficiencies by an order of magnitude or more.
       Efficiencies of synthesis past the abasic lesion depended strongly on
       the downstream (5'-neighboring) template base and on the properties of
       the polymerase. HIV-1 RT favored direct extension of X.A > X.G > X.T >
       X.C, by addition of the next correct nucleotide. However, it was found
       that X.C, least favored for direct extension, was most favored for
       misalignment extension, occurring when the DNA structure in the vicinity
       of the lesion collapsed to realign a primer 3'-C terminus opposite a
       downstream template G site. Polymerase properties have an important role
       in copying abasic lesions. Drosophila DNA polymerase alpha, HIV-1, and
       AMV reverse transcriptases had little difficulty inserting opposite
       abasic lesions, with efficiencies comparable to misinsertions opposite
       normal template bases. However, AMV RT did not extent past the lesion
       using direct or misalignment mechanisms. Wild-type and mutant T4 DNA
       polymerases were used to show that although exonucleolytic proofreading
       inhibits lesion bypass, the presence of a highly active proofreading
       exonuclease is not sufficient to prevent bypass.
 DE    *DNA Damage  *DNA Primers  *DNA Repair  Nucleotides  Support, Non-U.S.
       Gov't  Support, U.S. Gov't, P.H.S.  Templates  JOURNAL ARTICLE  REVIEW
       REVIEW, TUTORIAL

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