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. 2023 Jul 13;24(14):11412. doi: 10.3390/ijms241411412

Figure 2.

Figure 2

Molecular mechanism of pre-spliceosome complex assembly. (A) Schematic diagram of pre-spliceosome complex. The U2 snRNP associates with the pre-mRNA via binding to the BPS and its conformational changes begin to orient the pre-mRNA for ideal interaction with the U1 snRNP. (B) Displacement of SF1 by the ATPase activity of DDX39A/DDX39B (UAP56, Sub2 in yeast) allows for U2 snRNP to bind the branchpoint. DDX39A/DDX39B (UAP56, Sub2 in yeast) is stably bound to U2AF2. (C) Binding of U2 snRNP to the branchpoint sequence. The branchpoint adenosine sits in a pocket created by SF3B7 and SF3B1. SF3B1 interacts with the UHM domain of U2AF2. The SF3A complex forms a bridge-like structure between the SF3B complex and the Sm ring, stabilizing the U2 snRNP. (Created with BioRender.com (accessed on 12 May 2023)).