DNAASE ACTIVITIES IN EMBRYONIC CHICKEN LENS - IN EPITHELIAL-CELLS OR IN DIFFERENTIATING FIBERS WHERE CHROMATIN IS PROGRESSIVELY CLEAVED
DNAASE ACTIVITIES IN EMBRYONIC CHICKEN LENS - IN EPITHELIAL-CELLS OR IN DIFFERENTIATING FIBERS WHERE CHROMATIN IS PROGRESSIVELY CLEAVED
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DOI：
10.1111/j.1768-322x.1991.tb03020.x
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发表时间：
1991-01-01
影响因子：
2.7
通讯作者：
ALLINQUANT, B
中科院分区：
文献类型：
--
作者：
COUNIS, MF;CHAUDUN, E;ALLINQUANT, B
透镜是由一层上皮细胞和大量纤维组成的器官。 在终末分化过程中，赤道区的上皮细胞伸长成纤维，细胞核改变形状，染色质在分化的最后一步出现浓缩，DNA分解成核小体。 在不同鸡胚阶段（11和18天），使用凝胶基质中的DNA底物进行聚丙烯酰胺凝胶电泳，记录了DNA酶活性的模式[18，40]。 在两个阶段的透镜上皮细胞和纤维中观察到两种DNA酶（30和40 kDa）。 然而，这两种酶的活性在纤维细胞中增强。 30 kDa DNA酶需要Ca 2+和Mg 2+（5-15 mM）来水解DNA底物，而40 kDa活性被添加的二价阳离子（5-15 mM）抑制。 30 kDa蛋白被Na+抑制，可能是一种内切酶。 这两种核酸酶的活性可能都参与了纤维染色质在透镜终末分化过程中裂解成核小体的过程，但染色质构型、未掩蔽的DNA序列、阳离子的存在和pH梯度等变量可能决定了每种DNA酶的参与程度。
Lens is an organ composed of a layer of epithelial cells and a mass of fibers. During terminal differentiation, epithelial cells from the equatorial region elongate into fibers, nuclei change shape, the chromatin appears much condensed in the last step of differentiation and the DNA breaks down into nucleosomes. The pattern of DNAase activities has been recorded at different chick embryonic stages (11 and 18 days) using polyacrylamide gel electrophoresis with DNA substrate in the gel matrix [18, 40]. Two DNAases (30 and 40 kDa) have been observed in lens epithelia and fibers at both stages. However, the activities of both of the enzymes are augmented in fiber cells. The 30 kDa DNAase requires and Ca2+ and Mg2+ (5-15 mM) to hydrolyze the DNA substrate while the 40 kDa-activity is inhibited by added divalent cations (5-15 mM). The 30 kDa protein is inhibited by Na+ and is probably an endonuclease. Both nuclease activities probably are involved in the cleavage of fiber chromatin into nucleosomes during lens terminal differentiation, but variables such as chromatin configuration, unmasked DNA sequences, presence of cations, and pH gradients probably determine the extent of involvement of each DNAase.