Replication protein A induces the unwinding of long double-stranded DNA regions

被引:78
作者
Treuner, K [1 ]
Ramsperger, U [1 ]
Knippers, R [1 ]
机构
[1] UNIV KONSTANZ, DIV BIOL, D-78434 CONSTANCE, GERMANY
关键词
replication protein A; RPA-DNA complexes; DNA unwinding; electron microscopy; topoisomerase I;
D O I
10.1006/jmbi.1996.0305
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
We have investigated nucleoprotein filaments composed of human replication protein A (RPA) and DNA by electron microscopy. At low ionic strengths, RPA complexes with single-stranded DNA are similar in length to protein-free DNA suggesting that RPA-bound DNA remains in an extended configuration under these conditions. However, severe compaction of RPA-DNA complexes occurs in buffers with >2 mM MgCl2 or with 100 mM NaCl. At low ionic strengths, RPA binds to A + T-rich internal regions of linear double-stranded simian virus 40 (SV40) DNA and induces separation of complementary DNA strands. RPA also binds to closed-circular SV40 DNA, but requires the function of a DNA topoisomerase to invade and completely unwind duplex DNA regions. The ability of RPA to unwind long stretches of double-stranded DNA is not shared by the bacterial single-strand binding protein and the phage T4 gene 32 protein. (C) 1996 Academic Press Limited.
引用
收藏
页码:104 / 112
页数:9
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