Han S, Udvardy A, Schedl P
J Mol Biol. 1984 Nov 5;179(3):469-96. doi: 10.1016/0022-2836(84)90076-7.
We have examined the distribution of Neurospora crassa and S1 nuclease cleavage products in the chromatin of the 87A7 heat shock locus of Drosophila melanogaster. Both of these nucleases generate single and double-strand breaks in chromatin at specific sites in the 87A7 locus. Before heat induction, we find that the 5' ends of the two 87A7 hsp 70 genes contain N. crassa and S1 nuclease hypersensitive sites, while there are only a few cleavage products from elsewhere in the locus. With N. crassa nuclease, we observe one major 5' fragment, and this is derived from cleavage in a DNA segment mapping about 90 to 115 base-pairs from the beginning of the transcription unit. With S1 nuclease, we find two 5' cleavage products. The first maps about 120 to 130 base-pairs from the beginning of the gene. Interestingly, this site is also sensitive to S1 nuclease in supercoiled but not linear naked DNA. The other fragment maps very close to the transcription start site (approximately 0 to -15 base-pairs). After heat induction, there is a transition in the chromatin architecture of 87A7. First, there is a marked reduction in the yield of the prominent 5' N. crassa and S1 nuclease fragments. Second, the entire hsp 70 gene, as well as the spacer DNA just downstream from the 3' end of the gene, becomes highly sensitive to both of these nucleases.
我们研究了粗糙脉孢菌（Neurospora crassa）和S1核酸酶切割产物在黑腹果蝇（Drosophila melanogaster）87A7热休克基因座染色质中的分布。这两种核酸酶都会在87A7基因座的特定位点在染色质中产生单链和双链断裂。在热诱导之前，我们发现两个87A7热休克蛋白70（hsp 70）基因的5'端含有粗糙脉孢菌和S1核酸酶超敏感位点，而该基因座其他位置只有少量切割产物。使用粗糙脉孢菌核酸酶时，我们观察到一个主要的5'片段，它来自于转录单元起始处约90至115个碱基对的DNA片段中的切割。使用S1核酸酶时，我们发现两个5'切割产物。第一个位于基因起始处约120至130个碱基对处。有趣的是，该位点在超螺旋而非线性裸DNA中也对S1核酸酶敏感。另一个片段非常靠近转录起始位点（约0至 -15个碱基对）。热诱导后，87A7的染色质结构发生转变。首先，突出的5'粗糙脉孢菌和S1核酸酶片段的产量显著降低。其次，整个hsp 70基因以及基因3'端下游的间隔DNA对这两种核酸酶都变得高度敏感。
