Fas splicing regulation during early apoptosis is linked to caspase-mediated cleavage of U2AF65
Fas splicing regulation during early apoptosis is linked to caspase-mediated cleavage of U2AF65
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DOI：
10.1091/mbc.e07-11-1125
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发表时间：
2008-08-01
影响因子：
3.3
通讯作者：
Izquierdo, Jose M.
中科院分区：
文献类型：
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作者：
Izquierdo, Jose M.
U2 小核核糖核蛋白 (snRNP) 辅助因子 65 kDa (U2AF65) 是在剪接定型复合物组装过程中识别前 mRNA 3' 剪接位点的重要剪接因子。我们在此报道 U2AF65 在细胞凋亡过程中被蛋白水解。这种裂解依赖于位于天冬氨酸 (128) 残基周围的非规范单位点中的 I 组或 III 组 caspase，并导致 U2AF65 的 N 端和 C 端部分分离。 U2AF65 N 端片段主要积聚在核内的核内（核仁样模式），少量积聚在细胞质中，而 C 端片段则存在于细胞质中，甚至在细胞凋亡诱导的定位研究中也是如此。从功能角度来看，N 端片段通过充当 U2AF65 的显性失活版本，促进 Fas 外显子 6 从报告小基因中跳跃，而 C 端片段则没有显着影响。 U2AF65 N 末端片段的显性失活行为可以通过 U2AF35 过表达来恢复。有趣的是，Jurkat 细胞中 U2AF65 蛋白水解诱导早期细胞凋亡与内源性 Fas 外显子 6 内含物的下调相关。因此，这些结果支持细胞凋亡诱导、U2AF65 裂解和 Fas 选择性剪接调节之间的功能联系。
U2 small nuclear ribonucleoprotein (snRNP) auxiliary factor 65 kDa (U2AF65) is an essential splicing factor in the recognition of the pre-mRNA 3' splice sites during the assembly of the splicing commitment complex. We report here that U2AF65 is proteolyzed during apoptosis. This cleavage is group I or III caspase dependent in a noncanonical single site localized around the aspartic acid(128) residue and leads to the separation of the N- and C-terminal parts of U2AF65. The U2AF65 N-terminal fragment mainly accumulates in the nucleus within nuclear bodies (nucleoli-like pattern) and to a much lesser extent in the cytoplasm, whereas the C-terminal fragment is found in the cytoplasm, even in localization studies on apoptosis induction. From a functional viewpoint, the N-terminal fragment promotes Fas exon 6 skipping from a reporter minigene, by acting as a dominant-negative version of U2AF65, whereas the C-terminal fragment has no significant effect. The dominant-negative behavior of the U2AF65 N-terminal fragment can be reverted by U2AF35 overexpression. Interestingly, U2AF65 proteolysis in Jurkat cells on induction of early apoptosis correlates with the down-regulation of endogenous Fas exon 6 inclusion. Thus, these results support a functional link among apoptosis induction, U2AF65 cleavage, and the regulation of Fas alternative splicing.