Lin D, Chinault A C
Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030.
Somat Cell Mol Genet. 1988 May;14(3):261-72. doi: 10.1007/BF01534587.
To examine the association between chromatin structure and gene expression at the human hypoxanthine phosphoribosyltransferase (HPRT) locus, DNase I sensitivity of active and inactive genes was analyzed. In a set of human-hamster hybrid lines containing either an active or an inactive human X chromosome, or a derivative of the latter in which the HPRT gene was reactivated by 5-azacytidine treatment, only the promoter region of the gene was found to contain a hypersensitive domain, and its presence was strictly correlated with gene activity. An S1 nuclease-sensitive site was mapped upstream from the DNase I hypersensitive domain using supercoiled plasmids. The overall level of DNase I sensitivity in the interior of the HPRT gene was also assessed by comparing the degradation of polymorphic restriction fragments on active and inactive alleles in both polyclonal and monoclonal lines of female human cells. In these internally controlled experiments, the active X chromosome was found to be approximately twofold more susceptible to DNase I digestion than the inactive X chromosome.
为了研究人类次黄嘌呤磷酸核糖转移酶（HPRT）基因座处染色质结构与基因表达之间的关联，分析了活性基因和非活性基因对脱氧核糖核酸酶I（DNase I）的敏感性。在一组包含活性或非活性人类X染色体，或后者经5-氮杂胞苷处理后HPRT基因重新激活的衍生物的人-仓鼠杂交细胞系中，仅发现该基因的启动子区域含有一个超敏感结构域，且其存在与基因活性严格相关。使用超螺旋质粒在DNase I超敏感结构域上游定位了一个对S1核酸酶敏感的位点。通过比较女性人类细胞多克隆和单克隆系中活性和非活性等位基因上多态性限制性片段的降解情况，还评估了HPRT基因内部DNase I敏感性的总体水平。在这些内部控制实验中，发现活性X染色体对DNase I消化的敏感性比非活性X染色体高约两倍。
