Xiao S H, Manley J L
Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
EMBO J. 1998 Nov 2;17(21):6359-67. doi: 10.1093/emboj/17.21.6359.
SR proteins are a conserved family of splicing factors that function in both constitutive and activated splicing. We reported previously that phosphorylation of the SR protein ASF/SF2 enhances its interaction with the U1 snRNP-specific 70K protein and is required for the protein to function in splicing, while other studies have provided evidence that subsequent dephosphorylation can also be required for SR protein function, at least in constitutive splicing. We now show that the phosphorylation status of ASF/SF2 can differentially affect several properties of the protein. In keeping with a dynamic cycle of phosphorylation-dephosphorylation during splicing, ASF/SF2 phosphorylation was found to affect interaction with several putative protein targets in different ways: positively, negatively or not at all. Extending these results, we also show that, in contrast to constitutive splicing, dephosphorylation is not required for ASF/SF2 to function as a splicing activator. We discuss these results with respect to the differential protein-protein interactions that must occur during constitutive and activated splicing.
SR蛋白是一类保守的剪接因子家族，在组成型剪接和激活型剪接中均发挥作用。我们之前报道过，SR蛋白ASF/SF2的磷酸化增强了其与U1 snRNP特异性70K蛋白的相互作用，并且是该蛋白在剪接中发挥功能所必需的，而其他研究则提供了证据表明，至少在组成型剪接中，SR蛋白功能随后的去磷酸化也可能是必需的。我们现在表明，ASF/SF2的磷酸化状态可以不同地影响该蛋白的几种特性。与剪接过程中磷酸化-去磷酸化的动态循环一致，发现ASF/SF2磷酸化以不同方式影响与几种假定的蛋白质靶点的相互作用：正向、负向或完全无影响。扩展这些结果，我们还表明，与组成型剪接不同，ASF/SF2作为剪接激活剂发挥功能不需要去磷酸化。我们就组成型剪接和激活型剪接过程中必然发生的不同蛋白质-蛋白质相互作用来讨论这些结果。
