Galectin-3-U1 snRNP Complexes Initiate Splicing Activity in U1-Depleted Nuclear Extracts

Area of Science:

• Molecular Biology
• RNA Processing
• Gene Expression

Background:

• Uracil-rich small nuclear ribonucleoprotein complexes (U snRNP) are essential for pre-mRNA splicing.
• Galectin-3 is known to be involved in spliceosome assembly and splicing activity.

Purpose of the Study:

• To investigate the association between U snRNP and galectin-3.
• To determine the role of galectin-3-U1 snRNP complexes in initiating the splicing reaction.

Main Methods:

• Glycerol gradient centrifugation of HeLa cell nuclear extracts.
• Immunoprecipitation using galectin-3 specific antibodies.
• Depletion-reconstitution studies.
• Assay of splicing activity in U1-depleted nuclear extracts.

Main Results:

• Endogenous U snRNP complexes fractionate into various particles, with 10S complexes containing U1 snRNP and galectin-3.
• Galectin-3 specific antibodies coprecipitate U1 snRNP, confirming their association.
• Purified galectin-3-U1 snRNP complexes initiate splicing in U1-depleted extracts, forming intermediates and mature mRNA.

Conclusions:

• A fraction of U1 snRNP is associated with galectin-3 in nuclear extracts.
• The galectin-3-U1 snRNP complex serves as a potential entry point for galectin-3 into the splicing pathway.
• These complexes are capable of initiating the splicing reaction, highlighting their functional significance.