Synthetic DNA replication bubbles bound and unwound with twofold symmetry by a simian virus 40 T-antigen double hexamer.
Synthetic DNA replication bubbles bound and unwound with twofold symmetry by a simian virus 40 T-antigen double hexamer.
复制标题
合成 DNA 复制气泡通过猿猴病毒 40 T 抗原双六聚体以双重对称性结合和解开。
DOI：
10.1128/jvi.72.11.8676-8681.1998
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Borowiec,JA
中科院分区：
文献类型：
--
作者：
Smelkova,NV;Borowiec,JA
Dimerization of simian virus 40 T-antigen hexamers (TAgH) into double hexamers (TAgDH) on model DNA replication forks has been found to greatly stimulate T-antigen DNA helicase activity. To explore the interaction of TAgDHwith DNA during unwinding, we examined the binding of TAgDHto synthetic DNA replication bubbles. Tests of replication bubble substrates containing different single-stranded DNA (ssDNA) lengths indicated that efficient formation of a TAgDHrequires ≥40 nucleotides (nt) of ssDNA. DNase I probing of a substrate containing a 60-nt ssDNA bubble complexed with a TAgDHrevealed that T antigen bound the substrate with twofold symmetry. The strongest protection was observed over the 5′ junction on each strand, with 5 bp of duplex DNA and ∼17 nt of adjacent ssDNA protected from nuclease cleavage. Stimulation of the T-antigen DNA helicase activity by an increase in ATP concentration caused the protection to extend in the 5′ direction into the duplex region, while resulting in no significant changes to the 3′ edge of strongest protection. Our data indicate that each TAgHencircles one ssDNA strand, with a different strand bound at each junction. The process of DNA unwinding results in each TAgHinteracting with a greater length of DNA than was initially bound, suggesting the generation of a more highly processive helicase complex.
