Truter S L, Parker M I
Department of Medical Biochemistry, University of Cape Town Medical School, Observatory, South Africa.
J Cell Biochem. 1994 Feb;54(2):154-60. doi: 10.1002/jcb.240540204.
The higher ordered structure of the chicken alpha 2(1) procollagen gene was analyzed in chromatin isolated from expressing (lung) and nonexpressing (reticulocyte and erythrocyte) tissues. Digestion of DNA with methylation sensitive restriction endonucleases revealed that this gene was methylated in all tissues examined and that no differences existed in the promoter methylation patterns between expressing and nonexpressing tissues. DNAse 1 hypersensitive sites were located between 100-300 bp upstream from the transcription initiation site and within the first intron. These sites were also hypersensitive to the single-strand specific S1 nuclease, implying that this region of the gene in the chromatin is either in an unfolded single-stranded conformation or under severe conformational stress. These differences in the alpha 2(1) chromatin structure were confirmed by the finding that the promoter was more accessible to restriction endonuclease digestion in the expressing tissues than in the nonexpressing tissues. Digestion of chromatin with Pst I and Sma I revealed that some of these sites in the promoter were differentially protected by DNA-binding proteins in the two tissue types. These protected sites were located as far upstream as -1,600 and downstream within the first intron at +800.
对从表达组织（肺）和非表达组织（网织红细胞和红细胞）中分离出的染色质中的鸡α2(1)前胶原基因的高级结构进行了分析。用甲基化敏感的限制性内切酶消化DNA表明，该基因在所有检测的组织中均被甲基化，并且在表达组织和非表达组织之间的启动子甲基化模式没有差异。DNA酶I超敏感位点位于转录起始位点上游100 - 300 bp之间以及第一个内含子内。这些位点对单链特异性S1核酸酶也超敏感，这意味着染色质中该基因的这一区域要么处于未折叠的单链构象，要么处于严重的构象压力之下。α2(1)染色质结构的这些差异通过以下发现得到证实：与非表达组织相比，表达组织中的启动子对限制性内切酶消化更易接近。用Pst I和Sma I消化染色质表明，启动子中的一些位点在两种组织类型中受到DNA结合蛋白的不同保护。这些受保护的位点位于上游-1600处以及第一个内含子内下游+800处。
