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首页> 外文期刊>Journal of Virology >DNA Synthesis and Gene Expression in Bacillus subtilis Infected with Wild-Type and Hypermodification-Defective Bacteriophage SP10
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DNA Synthesis and Gene Expression in Bacillus subtilis Infected with Wild-Type and Hypermodification-Defective Bacteriophage SP10

机译：枯草芽孢杆菌中的DNA合成和基因表达用野生型和高修炼缺陷的噬菌体SP10感染

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摘要

A hypermodified base (Y-Thy) replaces 20% of the thymine (Thy) in mature DNA of Bacillus subtilis phage SP10. Two noncomplementing hypermodification-defective (hmd) mutants are described. At 30°C, hmd phage carried out a normal program, but at temperatures of ≥37°C, the infection process was nonproductive. When cells were infected at 37°C with hmd phage, DNA synthesis started at its usual time (12 min), proceeded at about half the normal rate for 6 to 8 min, and then stopped or declined manyfold. All, or nearly all, of the DNA made under hmd conditions consisted of fully hypermodified parental DNA strands H-bonded to unhypermodified nascent strands. The reduced levels of DNA synthesis observed under hmd conditions were accompanied by weak expression of late genes. A sucrose gradient analysis of SP10 hmd+ replicating DNA intermediates was made. Two intermediates, called VG and F, were identified. VF consisted of condensed DNA complexed to protein; VF also contained negatively supercoiled domains covalently joined to relaxed regions. F was composed of linear concatenates from which mature DNA was cleaved. None of those intermediates was evident in cells infected at 37°C with hmd phage. Shiftup experiments were performed wherein cells infected with hmd phage at 30°C were shifted to 37°C at a time when replication was well under way. DNA synthesis stopped or declined manyfold 10 min after shiftup. The hmd DNA made after shiftup was conserved as a form sedimentationally equivalent to the F intermediate, but little mature DNA was evident. It is proposed that Y-Thy is required for replication and DNA maturation because certain key proteins involved with these processes interact preferentially with hypermodified DNA.
机译：高型碱（Y-Thy）将20％的胸腺嘧啶（Thy）替代枯草芽孢杆菌的成熟DNA中的胸腺嘧啶（Thy）。描述了两种不合解的高修炼缺陷（ HMD ）突变体。在30°C时， HMD 噬菌体进行了正常程序，但在≥37°C的温度下，感染过程是非培养。当用 HMD 噬菌体感染细胞感染37℃时，DNA合成在通常的时间（12分钟）开始，在正常速率大约半下进行6至8分钟，然后停止或拒绝多重。在 HMD 条件下的所有DNA的全部或几乎所有的DNA都是由完全高补充的亲本DNA链组成，以粘合到无狗修饰的新生股线。在 HMD 条件下观察到的DNA合成水平降低伴随着晚期的弱表达。制备了SP10 HMD + 复制DNA中间体的蔗糖梯度分析。鉴定了两个称为VG和F的中间体。 VF由络合到蛋白质的浓缩DNA组成; VF还包含负面连接到松弛区域的负面超硅域。 F由成熟DNA切割的线性连接组成。没有其中这些中间体在37℃的细胞中显而易见，用 HMD 噬菌体感染。进行换档实验，其中在30℃下在30℃下感染的细胞在30℃下偏移至37℃。 DNA合成在换档后10分钟停止或拒绝多重。换档后的 HMD DNA被保守为沉积相当于F中间的形式，但很小的成熟DNA是显而易见的。提出了复制和DNA成熟所需的Y-Thy，因为这些方法所涉及的某些关键蛋白优先与过度补充DNA相互作用。

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