Nucleic Acids Research, Vol 25, Issue 9 1701-1708, Copyright © 1997 by Oxford University Press
N Nishikawa, N Kanda, M Oishi and R Kiyama
Oligo(dG).oligo(dC)- or short poly(dG).poly(dC)-containing fragments were
enriched and cloned by means of Mg2+-dependent triplex affinity capture and
subsequent cloning procedures. A library constructed after three cycles of
enrichment showed that approximately 80% of the clones in the supercoiled
form formed a complex with labeled oligonucleotide (dG)34. However, while
the rest of the clones retained the ability to form a complex (type I
clones), 90.9% failed to form a complex when they were linearized. This
group of DNA was abundant in the genomic DNA, although it showed only
approximately 3-fold enrichment by one cycle of affinity capture. This
group was further classified into two species (types II and III) based on
complex formation ability after phenol extraction. Type II clones retained
the complex formation ability after treatment, while the human telomere
[(TTAGGG)n] and telomere-like [(TGGAA)n] or [(TGGAG)n] sequences belonging
to type III clones did not. Serial deletion experiments and the binding
assays using oligonucleotides confirmed that the repetitive units
containing T(G)nT ( n = 3-5) tracts or (G)n-motifs (n >/= 3) were the
sites of complex formation for type II and III clones. On the other hand,
type I clones contained poly(dG).poly(dC) tracts at least 10 nt long, and
DNase I-footprinting analysis indicated that these tracts were the sites of
complex formation.
ARTICLES
Enrichment of oligo(dG).oligo(dC)-containing fragments from human genomic DNA by Mg 2+-dependent triplex affinity capture
Institute of Molecular and Cellular Biosciences, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113, Japan.
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