Samali A, Gilje B, Døskeland S O, Cotter T G, Houge G
Department of Biochemistry, University College Cork, Lee Maltings, Prospect Row, Cork, Ireland.
Cell Death Differ. 1997 May;4(4):289-93. doi: 10.1038/sj.cdd.4400246.
Discrete cleavages within 28S rRNA divergent domains have previously been found to coincide with DNA fragmentation during apoptosis. Here we show that rRNA and DNA cleavages can occur independently in apoptotic cells, i.e. that the previously observed correlation is likely to be coincidental. In HL-60 cells, apoptosis with massive DNA fragmentation could be induced without any signs of rRNA cleavage. The opposite situation; rRNA cleavage without concomitant internucleosomal DNA fragmentation, was found in okadaic acid-treated Molt-4 cells. Other leukemia cell lines underwent apoptosis either without (K562 and Molt-3) or with (U937) both forms of polynucleotide cleavage. In K562 cells transfected with a temperature-sensitive p53 mutant, internucleosomal DNA fragmentation but not 28S rRNA cleavage was inducible by wild-type p53 expression. The absence of apoptotic rRNA cleavage in some cell types suggests that this phenomenon is tightly regulated and unrelated to DNA fragmentation or a presumed scheme for general macromolecular degradation in apoptotic cells.
此前发现，28S rRNA 分歧区域内的离散切割与细胞凋亡过程中的 DNA 片段化同时发生。在此我们表明，rRNA 和 DNA 切割可在凋亡细胞中独立发生，即先前观察到的相关性可能是巧合。在 HL-60 细胞中，可诱导出具有大量 DNA 片段化的凋亡，而无任何 rRNA 切割迹象。相反的情况，即在冈田酸处理的 Molt-4 细胞中发现了 rRNA 切割而无伴随的核小体间 DNA 片段化。其他白血病细胞系在凋亡时，要么没有（K562 和 Molt-3），要么有（U937）两种形式的多核苷酸切割。在转染了温度敏感型 p53 突变体的 K562 细胞中，野生型 p53 表达可诱导核小体间 DNA 片段化，但不能诱导 28S rRNA 切割。某些细胞类型中凋亡性 rRNA 切割的缺失表明，这种现象受到严格调控，且与 DNA 片段化或凋亡细胞中一般大分子降解的假定模式无关。
