Wassarman K M, Steitz J A
Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06536-0812.
Genes Dev. 1993 Apr;7(4):647-59. doi: 10.1101/gad.7.4.647.
Psoralen cross-linking experiments in HeLa cell nuclear extracts have revealed the binding of U1 snRNA to substrates containing the SV40 late and adenovirus L3 polyadenylation signals. The sites of U1 cross-linking to the substrates map different distances upstream of the AAUAAA sequence to regions with limited complementarity to the 5' end of U1 snRNA. U1 cross-linking to the same site in the SV40 late pre-mRNA is enhanced by the addition of an upstream 3' splice site, which also enhances polyadenylation. Examination of different nuclear extracts reveals a correlation between U1 cross-linking and the coupling of splicing and polyadenylation, suggesting that the U1 snRNP participates in the coordination of these two RNA-processing events. Mutational analyses demonstrate that U1/substrate association cannot be too strong for coupling to occur and suggest that the U1 snRNP plays a similar role in recognition of internal and 3' terminal exons. Possible mechanisms for communication between the splicing and polyadenylation machineries are discussed, as well as how interaction of the U1 snRNP with 3' terminal exons might contribute to mRNA export.
在HeLa细胞核提取物中进行的补骨脂素交联实验表明，U1 snRNA与含有SV40晚期和腺病毒L3聚腺苷酸化信号的底物结合。U1与底物交联的位点在AAUAAA序列上游不同距离处，位于与U1 snRNA 5'端互补性有限的区域。通过添加上游3'剪接位点可增强U1与SV40晚期前体mRNA中同一位点的交联，这也会增强聚腺苷酸化。对不同核提取物的研究揭示了U1交联与剪接和聚腺苷酸化偶联之间的相关性，表明U1 snRNP参与了这两个RNA加工事件的协调。突变分析表明，U1/底物结合不能过强才能发生偶联，并表明U1 snRNP在识别内部和3'末端外显子中发挥类似作用。文中讨论了剪接和聚腺苷酸化机制之间可能的通讯机制，以及U1 snRNP与3'末端外显子的相互作用如何可能有助于mRNA输出。
