Cancer-associated SF3B1-K700E mutation controls immune responses by regulating Treg function via aberrant Anapc13 splicing | Science Advances

Recurrent somatic mutations in spliceosome factor 3b subunit 1 (SF3B1) are identified in hematopoietic malignancies, with SF3B1-K700E being the most common one. Here, we show that regulatory T cell (T _reg )–specific expression of SF3B1-K700E ( Sf3b1 ^K700Efl/+ /Foxp3 ^YFP-Cre ) results in spontaneous autoimmune phenotypes. CD4 ⁺ T cells from Sf3b1 ^K700Efl/+ /Foxp3 ^YFP-Cre mice display defective T _reg differentiation and inhibitory function, which is demonstrated by failed prevention of adoptive transfer colitis by Sf3b1 ^K700Efl/+ /Foxp3 ^YFP-Cre T _regs . Mechanically, SF3B1-K700E induces an aberrant splicing event that results in reduced expression of a cell proliferation regulator Anapc13 due to the insertion of a 231–base pair DNA fragment to the 5′ untranslated region. Forced expression of the Anapc13 gene restores the differentiation and ability of Sf3b1 ^K700Efl/+ /Foxp3 ^YFP-Cre T _regs to prevent adoptive transfer colitis. In addition, acute myeloid leukemia grows faster in aged, but not young, Sf3b1 ^K700Efl/+ /Foxp3 ^YFP-Cre mice compared to Foxp3 ^YFP-Cre mice. Our results highlight the impact of cancer-associated SF3B1 mutation on immune responses, which affect cancer development.