Abstract
Myelodysplastic syndromes (MDS) are haematopoietic malignancies that are characterised by a heterogeneous clinical course. In recent years, sequencing efforts have uncovered recurrent somatic mutations within RNA splicing factors, including SF3B1, SRSF2, U2AF1 and ZRSR2. The most frequently mutated gene is SF3B1, mutated in 17% of MDS patients. While SF3B1 mutations and their effects on splicing have been well characterised, much remains to be explored about their more far-reaching effects on cellular homeostasis. Given that mRNA splicing and nuclear export are coordinated processes, we hypothesised that SF3B1 mutation might also affect export of certain mRNAs and that this may represent a targetable pathway for the treatment of SF3B1-mutant MDS. We used CRISPR/Cas9-genome editing to create isogenic cellular models. Comprehensive transcriptome and proteome profiling of these cells identified alterations in the splicing and export of components of the translational machinery, primarily tRNA synthetases, in response to the SF3B1 K700E mutation. While steady-state protein synthesis was unaffected, SF3B1 mutant cells were more sensitive to the clinically-relevant purine analogue, 8-azaguanine. In this study, we also demonstrated that 8-azaguanine affects splicing. Our results suggest that the simultaneous targeting of RNA metabolism and splicing by 8-azaguanine represents a therapeutic opportunity for SF3B1-mutant myelodysplastic syndromes.
Highlights
Myelodysplastic syndromes (MDS) are myeloid haematopoietic malignancies that are characterised by an extremely heterogeneous clinical course, ranging from indolent disease without progression, to acute onset requiring immediate treatment
This sensitivity suggests that simultaneous targeting of both RNA metabolism and splicing by this single compound represents a therapeutic opportunity for patients suffering from SF3B1 mutant myelodysplastic syndromes
K-562 cells were edited using CRISPR/Cas[9] and single-stranded oligodeoxynucleotides to introduce an A > G substitution in codon 700 of the SF3B1 gene, the mutation observed in the majority of MDS patients
Summary
Myelodysplastic syndromes (MDS) are myeloid haematopoietic malignancies that are characterised by an extremely heterogeneous clinical course, ranging from indolent disease without progression, to acute onset requiring immediate treatment. While the connection between SF3B1 mutations and its effects on splicing at the molecular level has been well characterised[7], much remains to be explored about its more far-reaching effects on cell homeostasis. It has been known for many years that mRNA splicing and nuclear export are coordinated processes, that are tightly-linked[8,9,10]. While steady-state protein synthesis appears unaffected, SF3B1 mutant cells were more sensitive to the clinically-relevant purine analogue, 8-azaguanine This sensitivity suggests that simultaneous targeting of both RNA metabolism and splicing by this single compound represents a therapeutic opportunity for patients suffering from SF3B1 mutant myelodysplastic syndromes
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