Boulikas T, Kong C F
Institute of Molecular Medical Sciences, Palo Alto, California 94306.
J Cell Biochem. 1993 Sep;53(1):1-12. doi: 10.1002/jcb.240530102.
In order to understand the nature of DNA sequences that organize chromatin into domains or loops, we have cloned the nuclear matrix DNA (1.7% of the total DNA) from human myelogenous leukemia cells in culture. Nuclear matrix is formed by interactions between specific stretches of DNA of about 0.1 to 5.0 kb with protein transcription factors, nuclear enzymes, and structural proteins. Nuclear matrix is believed to be the exclusive nuclear microenvironment in which initiation of DNA replication, transcription, and repair take place. The matrix attachment regions (MARs) of DNA have transcriptional enhancer activity, harbor the origins of replication of the human genome, and define the borders between neighboring chromatin loops. In this study we report the sequence of the human MAR fragment 19.2 of a size of 542 bp. Hum. MAR 19.2 is composed of TG-, CA-, CT-, and GA-rich blocks and shows 8 perfect and imperfect inverted repeats. Thus, we have identified a novel class of MARs with sequence characteristics divergent from the AT-rich class of MARs. The inverted repeats of the 19.2 sequence might be stabilized into their cruciform configuration by torsional strain and by specific transcription/replication protein factors. This MAR might function in the initiation of replication of the flanking chromatin domain and in the regulation of the transcriptional activity of the gene(s) that reside in this domain.
为了了解将染色质组织成结构域或环的DNA序列的性质，我们从培养的人骨髓性白血病细胞中克隆了核基质DNA（占总DNA的1.7%）。核基质是由约0.1至5.0 kb的特定DNA片段与蛋白质转录因子、核酶和结构蛋白相互作用形成的。核基质被认为是DNA复制、转录和修复起始发生的唯一核微环境。DNA的基质附着区域（MARs）具有转录增强子活性，包含人类基因组的复制起点，并界定相邻染色质环之间的边界。在本研究中，我们报告了大小为542 bp的人类MAR片段19.2的序列。人类MAR 19.2由富含TG、CA、CT和GA的区域组成，并显示出8个完美和不完美的反向重复序列。因此，我们鉴定出了一类新型的MARs，其序列特征与富含AT的MARs类不同。19.2序列的反向重复序列可能通过扭转应变和特定的转录/复制蛋白因子稳定成十字形结构。这个MAR可能在侧翼染色质结构域的复制起始以及位于该结构域的基因转录活性调控中发挥作用。
