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J. Virol., Aug 1995, 4683-4692, Vol 69, No. 8
SP Moore, M Powers and DJ Garfinkel
Integration of the Saccharomyces cerevisiae retrotransposon Ty1 requires
the element-encoded integrase (IN) protein, which is a component of
cytoplasmic virus-like particles (VLPs). Using purified recombinant Ty1 IN
and an oligonucleotide integration assay based on Ty1 long terminal repeat
sequences, we have compared IN activity on substrates having either
wild-type or altered donor ends. IN showed a marked preference for
blunt-end substrates terminating in an A:T pair over substrates ending in a
G:C pair or a 3' dideoxyadenosine. VLP activity on representative
substrates also showed preference for donor strands which have an adenosine
terminus. Staggered-end substrates showed little activity when nucleotides
were removed from the end of the wild-type donor strand, but removal of one
nucleotide from the complementary strand did not significantly diminish
activity. Removal of additional nucleotides from the complementary strand
reduced activity to minimal detection levels. These results suggest that
the sequence specificity of Ty1 IN is not stringent in vitro. The absence
of Ty1 IN-mediated 3' dinucleotide cleavage, a characteristic of retroviral
integrases, was demonstrated by using selected substrates. In addition to
the forward reaction, both recombinant IN and VLP- associated IN carry out
the reverse disintegration reaction with long terminal repeat-based
dumbbell substrates. Disintegration activity exhibits sequence preferences
similar to those observed for the forward reaction.
Copyright © 1995, American Society for Microbiology
Substrate specificity of Ty1 integrase
ABL-Basic Research Program, NCI-Frederick Cancer Research and Development Center, Maryland 21702-1201, USA.
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