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Published on: April 26, 2017
Characterization of the aberrant splicing of DVL2 induced by cancer-associated SF3B1 mutation
Bo Zhao1, Xin Hu2, Yuning Zhou3
1China-Japan Union Hospital of Jilin University, Jilin University, Changchun, Jilin, 130033, China; School of Life Sciences, Jilin University, Changchun, Jilin, 130012, China.
Abstract:
SF3B1, an essential component of the U2 snRNP, is frequently mutated in cancers. Cancer-associated SF3B1 mutation causes aberrant RNA splicing, mostly at 3' splice sites (3'ss). RNA splicing of DVL2, a regulator of Notch signaling, is affected by SF3B1 mutation. Here, we report that the mutated SF3B1 use an alternative branchpoint sequence (BPS) for the aberrant splicing of DVL2, which has a higher affinity to U2 snRNA than the BPS for the canonical splicing of DVL2. Swapping the position of the alternative BPS with the position of the canonical BPS decreased the aberrant splicing of DVL2, suggesting that the mutated SF3B1 prefers to use BPS with high affinity to U2 snRNA for splicing. Additionally, swapping the positions of two BPSs associated with the canonical splicing of DVL2 demonstrated that both the affinity to the U2 snRNA and the distance to the 3'ss are important to the selection of BPS. Importantly, the aberrant splicing of DVL2 does not require the canonical 3'ss and the canonical polypyrimidine tract, which reveals a novel type of aberrant splicing induced by SF3B1 mutation. These findings provide a more comprehensive understanding of the mechanisms underlying aberrant splicing induced by SF3B1 mutation in cancer.
Insights
Mutated SF3B1 in cancer uses a high-affinity alternative branchpoint sequence for aberrant DVL2 splicing. This novel mechanism bypasses canonical splicing signals, offering new insights into cancer-associated splicing defects.
Area of Science:
- Molecular Biology
- Cancer Biology
- RNA Splicing
Background:
- SF3B1 (Splicing Factor 3B Subunit 1) is crucial for U2 snRNP function and frequently mutated in various cancers.
- SF3B1 mutations lead to aberrant RNA splicing, primarily affecting 3' splice sites (3'ss).
- DVL2, a key regulator of Notch signaling, is among the genes whose splicing is altered by SF3B1 mutations.
Purpose of the Study:
- To elucidate the specific mechanism by which SF3B1 mutations induce aberrant splicing of DVL2.
- To investigate the role of branchpoint sequences (BPS) and their affinity to U2 snRNA in SF3B1-mediated aberrant splicing.
- To characterize the novel splicing events associated with DVL2 in the context of SF3B1 mutations.
Main Methods:
- Comparative analysis of wild-type and mutated SF3B1 activity on DVL2 splicing.
- Site-directed mutagenesis to swap canonical and alternative BPS positions within DVL2.
- Assessment of BPS affinity to U2 snRNA.
- Evaluation of the requirement for canonical 3'ss and polypyrimidine tract in aberrant splicing.
Main Results:
- Mutated SF3B1 utilizes an alternative BPS for DVL2 splicing, exhibiting higher affinity to U2 snRNA than the canonical BPS.
- Altering the position of the alternative BPS significantly reduced aberrant DVL2 splicing, indicating a preference for high-affinity BPS.
- Both BPS affinity to U2 snRNA and its distance to the 3'ss are critical for BPS selection during splicing.
- Aberrant DVL2 splicing induced by SF3B1 mutation does not necessitate the canonical 3'ss or polypyrimidine tract.
Conclusions:
- SF3B1 mutations can induce a novel form of aberrant RNA splicing in DVL2 by favoring alternative, high-affinity branchpoint sequences.
- This mechanism highlights the importance of BPS characteristics (affinity and position) in determining splicing outcomes.
- The findings deepen the understanding of SF3B1's role in cancer-associated splicing dysregulation and offer potential therapeutic targets.
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