Dixon D K, Jones D, Candido E P
Carnegie Institution of Washington, Department of Embryology, Baltimore, MD 21210.
DNA Cell Biol. 1990 Apr;9(3):177-91. doi: 10.1089/dna.1990.9.177.
The 16-kD heat shock genes of Caenorhabditis elegans are encoded by four highly similar genes, arranged as divergently transcribed pairs. In spite of the high level of identity that exists between the HSP16 genes, after 2 hr of heat shock the mRNA from one locus accumulates at 7-14 times the level of that from the other locus. To determine if differential HSP16 gene transcriptional activity contributes to these differences, we examined the chromatin structure of the HSP16 genes in nonshocked embryos and in embryos undergoing both the initial phases of heat shock and after 2 hr of heat shock. To carry out these studies, we developed a nuclei isolation procedure that has allowed us to prepare large amounts of nuclei from C. elegans embryos, larvae, and adults that are essentially free of endogenous nuclease and protease activities and appear to be an excellent substrate for investigating chromatin structure in C. elegans. This procedure has enabled us to report the first observations of C. elegans basic chromatin structure, as well as characterize HSP16 chromatin structure in detail. The data suggest that differential HSP16 RNA accumulation following 2 hr of heat shock appears to be correlated with a change in the chromatin structure of one of the HSP16 loci to a preinduction, transcriptionally inactive configuration.
秀丽隐杆线虫的16-kD热休克基因由四个高度相似的基因编码，它们以反向转录对的形式排列。尽管HSP16基因之间存在高度的同一性，但在热休克2小时后，一个位点的mRNA积累水平是另一个位点的7 - 14倍。为了确定HSP16基因转录活性的差异是否导致了这些差异，我们检查了未受冲击的胚胎以及处于热休克初始阶段和热休克2小时后的胚胎中HSP16基因的染色质结构。为了进行这些研究，我们开发了一种细胞核分离程序，该程序使我们能够从秀丽隐杆线虫的胚胎、幼虫和成虫中制备大量的细胞核，这些细胞核基本上没有内源性核酸酶和蛋白酶活性，似乎是研究秀丽隐杆线虫染色质结构的理想底物。这个程序使我们能够首次观察秀丽隐杆线虫的基本染色质结构，并详细表征HSP16染色质结构。数据表明，热休克2小时后HSP16 RNA积累的差异似乎与其中一个HSP16位点的染色质结构变化有关，该变化转变为诱导前转录无活性的构型。
