DHX15 is involved in SUGP1-mediated RNA missplicing by mutant SF3B1 in cancer

Area of Science:

• Molecular Biology
• Cancer Genetics
• RNA Splicing Mechanisms

Background:

• The spliceosomal gene SF3B1 is the most frequently mutated splicing factor in cancer.
• Mutations in SF3B1 disrupt its interaction with SUGP1, leading to characteristic RNA missplicing in cancer.
• SUGP1's G-patch motif suggests a requirement for a DEAH-box RNA helicase in its splicing function.

Purpose of the Study:

• To identify the specific RNA helicase that interacts with SUGP1.
• To elucidate the role of this helicase in SF3B1-mutant cancer splicing defects.
• To understand the structural basis of the DHX15-SUGP1 interaction.

Main Methods:

• Protein-protein interaction assays.
• Depletion and mutation studies of DHX15.
• Spliceosome incorporation assays.
• Crystal structure determination of the DHX15-SUGP1 complex.

Main Results:

• DHX15 was identified as the critical RNA helicase interacting with SUGP1.
• DHX15 depletion or mutation partially mimicked SF3B1 mutant splicing defects.
• A DHX15-SUGP1 fusion protein rescued splicing defects in SF3B1-mutant contexts.
• The crystal structure revealed the molecular basis of the DHX15-SUGP1 interaction.

Conclusions:

• DHX15 is the RNA helicase that functions with SUGP1 in RNA splicing.
• Mutant SF3B1 disrupts splicing by interfering with the DHX15-SUGP1 complex.
• This work provides insight into the mechanism of SF3B1-driven splicing dysregulation in cancer.