Structure of the activated human minor spliceosome

Area of Science:

• Molecular Biology
• Structural Biology
• RNA Biology

Background:

• The minor spliceosome is essential for splicing U12-type precursor messenger RNA (pre-mRNA), a rare but critical process.
• Understanding the structural basis of minor spliceosome function is key to comprehending gene expression regulation.

Purpose of the Study:

• To determine the atomic features of the activated human minor spliceosome.
• To elucidate the roles of specific proteins and small nuclear RNAs (snRNAs) in minor spliceosome assembly and function.

Main Methods:

• Cryo-electron microscopy (cryo-EM) at 2.9-angstrom resolution.
• Structural analysis of the activated human minor spliceosome complex.

Main Results:

• The atomic structure of the activated human minor spliceosome was determined.
• U6atac and U12 small nuclear RNAs (snRNAs) were shown to recognize the 5' splice site and branch point sequence, respectively.
• Five novel proteins (SCNM1, RBM48-ARMC7, PPIL2, and CRIPT) were identified as crucial stabilizers of the catalytic center and small nuclear ribonucleoprotein (snRNP) complexes.

Conclusions:

• The study provides a high-resolution structural framework for the human minor spliceosome.
• Identified proteins play critical roles in stabilizing the catalytic core and specific snRNPs, offering mechanistic insights into U12-type splicing.
• This work lays the groundwork for understanding the functional mechanisms of the human minor spliceosome.