Crispino J D, Sharp P A
Massachusetts Institute of Technology, Center for Cancer Research, Cambridge 02139-4307, USA.
Genes Dev. 1995 Sep 15;9(18):2314-23. doi: 10.1101/gad.9.18.2314.
The full set of consensus sequences at the 5' splice site is recognized during splicing of pre-mRNA in extracts depleted of U1 snRNP. High concentrations of HeLa SR proteins or purified SC35 alone promote the splicing of specific RNA substrates, bypassing the requirement for U1 snRNP in formation of the U2 snRNP-pre-mRNA complex. Under these conditions, mutations in the substrate that increase the sequence complementarity between U6 snRNA and the 5' splice site region can facilitate splicing. This provides additional strong evidence that U1 snRNP is not essential for splicing. Thus, the consensus sequence at the 5' splice site is probably recognized twice during splicing of most introns; however, some pre-mRNAs could potentially be processed in the absence of interactions with U1 snRNP in regions of the nucleus containing high concentrations of SR protein.
在去除U1 snRNP的提取物中进行前体mRNA剪接时，5'剪接位点的全套共有序列会被识别。高浓度的HeLa SR蛋白或单独纯化的SC35可促进特定RNA底物的剪接，绕过U1 snRNP在形成U2 snRNP-前体mRNA复合物中的需求。在这些条件下，底物中增加U6 snRNA与5'剪接位点区域之间序列互补性的突变可促进剪接。这提供了额外的有力证据，表明U1 snRNP对剪接并非必不可少。因此，在大多数内含子剪接过程中，5'剪接位点的共有序列可能会被识别两次；然而，一些前体mRNA在含有高浓度SR蛋白的细胞核区域中，可能在不与U1 snRNP相互作用的情况下进行加工。
