ABSTRACT
Recurrent mutations in the spliceosome are observed in several human cancers, but their functional and therapeutic significance remains elusive. SF3B1, the most frequently mutated component of the spliceosome in cancer, is involved in the recognition of the branch point sequence (BPS) during selection of the 3' splice site (ss) in RNA splicing. Here, we report that common and tumor-specific splicing aberrations are induced by SF3B1 mutations and establish aberrant 3' ss selection as the most frequent splicing defect. Strikingly, mutant SF3B1 utilizes a BPS that differs from that used by wild-type SF3B1 and requires the canonical 3' ss to enable aberrant splicing during the second step. Approximately 50% of the aberrantly spliced mRNAs are subjected to nonsense-mediated decay resulting in downregulation of gene and protein expression. These findings ascribe functional significance to the consequences of SF3B1 mutations in cancer.
Subject(s)
Alternative Splicing , Mutation , Neoplasms/genetics , Phosphoproteins/genetics , Ribonucleoprotein, U2 Small Nuclear/genetics , Alleles , Amino Acid Sequence , Base Sequence , HEK293 Cells , Humans , Molecular Sequence Data , Mutation Rate , Nonsense Mediated mRNA Decay , Phosphoproteins/chemistry , Phosphoproteins/metabolism , RNA Splicing Factors , Ribonucleoprotein, U2 Small Nuclear/chemistry , Ribonucleoprotein, U2 Small Nuclear/metabolismABSTRACT
A total synthesis of the natural product 6-deoxypladienolide D (1) has been achieved. Two noteworthy attributes of the synthesis are (1) a late-stage allylic oxidation which proceeds with full chemo-, regio-, and diastereoselectivity and (2) the development of a scalable and cost-effective synthetic route to support drug discovery efforts. 6-Deoxypladienolide D (1) demonstrates potent growth inhibition in a mutant SF3B1 cancer cell line, high binding affinity to the SF3b complex, and inhibition of pre-mRNA splicing.
Subject(s)
Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/pharmacology , Cell Line, Tumor/chemistry , Cell Line, Tumor/drug effects , Cell Proliferation/drug effects , Epoxy Compounds/chemical synthesis , Epoxy Compounds/metabolism , Macrolides/chemical synthesis , Macrolides/metabolism , Phosphoproteins/antagonists & inhibitors , Phosphoproteins/chemistry , RNA Splicing/drug effects , Ribonucleoprotein, U2 Small Nuclear/antagonists & inhibitors , Ribonucleoprotein, U2 Small Nuclear/chemistry , Antineoplastic Agents/chemistry , Binding Sites , Epoxy Compounds/chemistry , Humans , Macrolides/chemistry , RNA Splicing FactorsABSTRACT
The total synthesis of kalihinol C, a bis-isonitrile marine diterpenoid isolated from Acanthella sp., is reported. The decalin framework was established via an intramolecular Diels-Alder cycloaddition and subsequently functionalized through a series of substrate-controlled diastereoselective transformations to install the tertiary isonitrile, beta-hydroxy isonitrile, and pendant tetrahydrofuranyl ring.
