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首页> 外文期刊>Molecular and Cellular Biology >Matrix attachment regions are positioned near replication initiation sites, genes, and an interamplicon junction in the amplified dihydrofolate reductase domain of Chinese hamster ovary cells.
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Matrix attachment regions are positioned near replication initiation sites, genes, and an interamplicon junction in the amplified dihydrofolate reductase domain of Chinese hamster ovary cells.

机译：基质附着区域位于中国仓鼠卵巢细胞的扩增的二氢叶酸还原酶结构域中的复制起始位点，基因和两性间连接附近。

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摘要

Genomic DNA in higher eucaryotic cells is organized into a series of loops, each of which may be affixed at its base to the nuclear matrix via a specific matrix attachment region (MAR). In this report, we describe the distribution of MARs within the amplified dihydrofolate reductase (DHFR) domain (amplicon) in the methotrexate-resistant CHO cell line CHOC 400. In one experimental protocol, matrix-attached and loop DNA fractions were prepared from matrix-halo structures by restriction digestion and were analyzed for the distribution of amplicon sequences between the two fractions. A second, in vitro method involved the specific binding to the matrix of cloned DNA fragments from the amplicon. Both methods of analysis detected a MAR in the replication initiation locus that we have previously defined in the DHFR amplicon, as well as in the 5'-flanking region of the DHFR gene. The first of these methods also suggests the presence of a MAR in a region mapping approximately 120 kilobases upstream from the DHFR gene. Each of these MARs was detected regardless of whether the matrix-halo structures were prepared by the high-salt or the lithium 3,5-diiodosalicylate extraction protocols, arguing against their artifactual association with the proteinaceous scaffolding of the nucleus during isolation procedures. However, the in vitro binding assay did not detect the MAR located 120 kilobases upstream from the DHFR gene but did detect specific matrix attachment of a sequence near the junction between amplicons. The results of these experiments suggest that (i) MARs can occur next to different functional elements in the genome, with the result that a DNA loop formed between two MARs can be smaller than a replicon; and (ii) different methods of analysis detect a somewhat different spectrum of matrix-attached DNA fragments.
机译：高等真核细胞中的基因组DNA被组织成一系列环，每个环可以通过特定的基质附着区（MAR）固定在核基质上。在这份报告中，我们描述了抗甲氨蝶呤的CHO细胞系CHOC 400中MARs在扩增的二氢叶酸还原酶（DHFR）域（amplicon）中的分布。在一项实验方案中，从基质-通过限制性消化的卤素结构，并分析了两个部分之间扩增子序列的分布。第二种体外方法涉及特异性结合从扩增子克隆的DNA片段的基质。两种分析方法均在我们先前在DHFR扩增子以及DHFR基因的5'侧翼区域中定义的复制起始位点中检测到MAR。这些方法中的第一种还表明在DHFR基因上游约120千碱基的区域中存在MAR。无论是通过高盐还是3,5-二碘代水杨酸锂提取方案制备了基质-卤代结构，都检测到了每个MAR，认为它们在分离过程中与核的蛋白质骨架在人为方面存在联系。但是，体外结合测定法未检测到位于DHFR基因上游120公里碱基处的MAR，但未检测到扩增子之间连接附近序列的特定基质附着。这些实验的结果表明：（i）MARs可以发生在基因组中不同功能元件的旁边，结果两个MARs之间形成的DNA环可以小于复制子。 （ii）不同的分析方法可以检测出与基质连接的DNA片段的光谱有所不同。

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