J Biol Chem, Vol. 274, Issue 47, 33313-33319, November 19, 1999
Strand Asymmetry of +1 Frameshift Mutagenesis at a Homopolymeric
Run by DNA Polymerase III Holoenzyme of Escherichia
coli
Mineaki
Seki
§,
Masahiro
Akiyama¶,
Yutaka
Sugaya
,
Eiichi
Ohtsubo§, and
Hisaji
Maki
§
From the
Department of Molecular Biology, Graduate
School of Biological Sciences, Nara Institute of Science and
Technology, Ikoma, Nara 630-0101, Japan, the ¶ Department of
Biochemistry, Stanford University School of Medicine, Stanford,
California 94305-5307, and the § Institute of Molecular and
Cellular Biosciences, The University of Tokyo, Bunkyo-ku,
Tokyo 113-0032, Japan
We have recently shown that single-base
frameshifts were predominant among mutations induced within the
rpsL target sequence upon oriC plasmid DNA
replication in vitro. We found that the occurrence of +1
frameshifts at a run of 6 residues of dA/dT could be increased
proportionally by increasing the concentration of dATP present in the
in vitro replication. Using single-stranded circular DNA
containing either the coding sequence of the rpsL gene or
its complementary sequence, the +1 frameshift mutagenesis by DNA
polymerase III holoenzyme of Escherichia coli was
extensively examined. A6
A7
frameshifts occurred 30 to 90 times more frequently during
DNA synthesis with the noncoding sequence (dT tract) template than with the coding sequence (dA tract). Excess dATP
enhanced the occurrence of +1 frameshifts during DNA synthesis with the dT tract template, but no other dNTPs showed such an effect. In the
presence of 0.1 mM dATP, the A6
A7 mutagenesis with the dT tract template was not inhibited
by 1.5 mM dCTP, which is complementary to the residue
immediately upstream of the dT tract. These results strongly suggested
that the A6
A7 frameshift mutagenesis
possesses an asymmetric strand nature and that slippage errors leading
to the +1 frameshift are made during chain elongation within the tract
rather than by misincorporation of nucleotides opposite residues next
to the tract.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.