title: SF3b1 mutations associated with myelodysplastic syndromes alter the fidelity of branchsite selection in yeast.
abstract: RNA and protein components of the spliceosome work together to identify the 5΄ splice site, the 3΄ splice site, and the branchsite (BS) of nascent pre-mRNA. SF3b1 plays a key role in recruiting the U2 snRNP to the BS. Mutations in human SF3b1 have been linked to many diseases such as myelodysplasia (MDS) and cancer. We have used SF3b1 mutations associated with MDS to interrogate the role of the yeast ortholog, Hsh155, in BS selection and splicing. These alleles change how the spliceosome recognizes the BS and alter splicing when nonconsensus nucleotides are present at the -2, -1 and +1 positions relative to the branchpoint adenosine. This indicates that changes in BS usage observed in humans with SF3b1 mutations may result from perturbation of a conserved mechanism of BS recognition. Notably, different HSH155 alleles elicit disparate effects on splicing: some increase the fidelity of BS selection while others decrease fidelity. Our data support a model wherein conformational changes in SF3b1 promote U2 association with the BS independently of the action of the DEAD-box ATPase Prp5. We propose that SF3b1 functions to stabilize weak U2/BS duplexes to drive spliceosome assembly and splicing.
authors.affiliation: Department of Biochemistry, U. Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Tucker J
authors.initials: TJ
authors.lastname: Carrocci
authors.affiliation: Department of Biochemistry, U. Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Zoerner
authors.affiliation: Department of Biochemistry, U. Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Joshua C
authors.initials: JC
authors.lastname: Paulson
authors.affiliation: Department of Biochemistry, U. Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Aaron A
authors.initials: AA
authors.lastname: Hoskins
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics; D053487:DEAD-box RNA Helicases / Q000235:genetics*; D006801:Humans; D009154:Mutation; D009190:Myelodysplastic Syndromes / Q000235:genetics* / Q000473:pathology; D010750:Phosphoproteins / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics; D000072260:RNA Splicing Factors / Q000235:genetics*; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D017381:Spliceosomes / Q000235:genetics
chemical_list: C405527:HSH155 protein, S cerevisiae; D010750:Phosphoproteins; D000072260:RNA Splicing Factors; D017413:Ribonucleoprotein, U2 Small Nuclear; C112491:SF3B1 protein, human; D029701:Saccharomyces cerevisiae Proteins; D000251:Adenosine Triphosphatases; C467585:DDX46 protein, human; C064447:PRP5 protein, S cerevisiae; D053487:DEAD-box RNA Helicases