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

Area of Science:

• Molecular Biology
• Genetics
• Cancer Biology

Background:

• Mutations in SF3B1, a U2 snRNP protein, are linked to myelodysplastic syndromes and other cancers.
• The K700E mutation in SF3B1 disrupts interactions with SUGP1, leading to aberrant splice site activation.

Purpose of the Study:

• To investigate the impact of the SF3B1 K700E mutation on branch site (BS) recognition using U2 IP-seq.
• To understand how this mutation affects spliceosome function and gene expression in leukemia cells.

Main Methods:

• Application of U2 IP-seq to profile branch site binding across the transcriptome.
• Analysis of K562 leukemia cells carrying the SF3B1 K700E mutation.

Main Results:

• Identified shifted branch sites associated with cryptic 3' splice sites activated by the K700E mutation.
• Discovered thousands of additional changes in branch site binding, often near natural sites, without altering 3' splice site choice.
• Observed that new branch sites exhibit stronger U2 snRNA base-pairing potential or are near stronger polypyrimidine tracts.

Conclusions:

• The SF3B1 K700E mutation induces widespread imprecision in branch site recognition.
• Limited changes in 3' splice site selection suggest a positive role for SUGP1 in early branch site choice.
• These findings expand the understanding of the physiological consequences of this oncogenic SF3B1 mutation.