Cancer-associated SF3B1 mutation K700E causes widespread changes in U2/branchpoint recognition without altering...

Area of Science:

• Molecular Biology
• Genetics
• Cancer Research

Background:

• Mutations in the U2 snRNP protein SF3B1 are frequently observed in myelodysplastic syndromes and other cancers.
• Specific mutations, such as K700E, disrupt protein interactions and lead to aberrant alternative 3' splice site activation, likely due to altered branch site recognition by the spliceosome.

Purpose of the Study:

• To investigate the impact of the SF3B1 K700E mutation on branch site (BS) recognition across the transcriptome.
• To identify changes in BS binding associated with aberrant alternative 3' splice site (ss) selection.

Main Methods:

• Utilized U2 immunoprecipitation sequencing (IP-seq) to profile branch site binding.
• Analyzed K562 leukemia cells harboring the SF3B1 K700E mutation.

Main Results:

• Identified shifted branch sites associated with alternative 3' splice sites activated by the K700E mutation.
• Discovered thousands of additional changes in branch site binding in mutant cells that do not alter splicing.
• Observed that these novel branch sites are proximal to natural sites and possess enhanced U2 snRNA base-pairing potential or stronger polypyrimidine tracts.

Conclusions:

• The SF3B1 K700E mutation induces widespread imprecision in branch site recognition.
• This imprecision in branch site recognition, with limited changes in 3' splice site selection, broadens the known physiological consequences of this oncogenic mutation.