Multiple initiation sites within the human ribosomal RNA gene
Multiple initiation sites within the human ribosomal RNA gene
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DOI：
10.4161/cc.5.11.2814
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发表时间：
2006-06-01
期刊：
影响因子：
4.3
通讯作者：
Cohen, Stanley
中科院分区：
文献类型：
--
作者：
Coffman, Frederick D.;He, Mai;Cohen, Stanley
大量研究表明，DNA 复制起始于人类核糖体 RNA 基因 (rDNA) 的 30 kB 非转录间隔区 (NTS)。使用一系列紧密间隔的引物对来测量通过离心淘洗分离的中期和晚期 S 期细胞中新生前导链的丰度，我们发现了 NTS 6 kb 区域内一个高度优选的起始位点和两个较少使用的位点的证据。起始位点与重要的 DNA 解旋元件 (DUE)、基质附着区 (MAR) 和 ARS 样序列共定位。通过循环排列分析将内在 DNA 弯曲位点定位在一个起始位点的数百个碱基对范围内。虽然 DUE 和 MAR 元件出现在整个 43 kb rDNA 序列的其他位置，但 DUE 和 MAR 元件的紧密关联仅发生在复制起始位点附近，这种并置也出现在其他经过充分研究的哺乳动物复制起始位点中。在 S 期中后期，靠近 DUE 和 MAR 元件的 rDNA 起始位点的利用，但不是如之前所示的在非常早期的 S 期，表明在 rRNA 基因中，这些序列相关特性的贡献可能对与转录不活跃基因相关的起始位点比对与转录活跃基因相关的起始位点更重要。
Numerous studies have demonstrated that DNA replication initiates within the 30 kB non-transcribed spacer (NTS) region of the human ribosomal RNA gene ( rDNA). Using a series of closely spaced primer pairs to measure nascent leading strand abundance in mid and late S phase cells isolated by centrifugal elutriation, we find evidence for one highly preferred initiation site and two less utilized sites within a 6 kb region of the NTS. The initiation sites colocalize with significant DNA unwinding elements (DUEs), matrix attachment regions (MARs), and ARS-like sequences. An intrinsic DNA bending site was localized by circular permutation analysis to within several hundred base pairs of one initiation site. While DUE and MAR elements occur elsewhere throughout the 43 kb rDNA sequence, the close association of DUE and MAR elements occurs only near replication initiation sites, a juxtaposition also seen in other well-studied mammalian replication initiation sites. The utilization of rDNA initiation sites close to DUE and MAR elements in mid and late S phase, but not in very early S phase as previously shown, suggests that in rRNA genes, contributions from these sequence-associated properties may be more significant to initiation sites associated with transcriptionally inactive genes, than to initiation sites associated with transcriptionally active genes.