MacroH2A1.1 mRNA levels are significantly decreased in patients with low-risk MDS presenting with chromosomal 5q deletion and myeloid cytopenias and tend to be decreased in MDS patients carrying the U2AF1 S34F mutation.
Taken together, our results demonstrate that ATR may represent a novel therapeutic target in patients with MDS carrying the U2AF1(S34F) mutation and potentially other malignancies harboring spliceosome mutations.<b>Significance:</b> This study provides preclinical evidence that patients with MDS or other myeloid malignancies driven by spliceosome mutations may benefit from ATR inhibition to exploit the R loop-associated vulnerability induced by perturbations in splicing.<i></i>.
We infer that U2AF1 S34 mutations characterize a distinct subgroup of MDS: younger age of onset and differential associations with particular cytogenetic aberrations depending on specific mutations [S34Y to +8; S34F to +8 and del(20q)].
MDS and acute myeloid leukemia patient samples harboring U2AF35(S34F) have a similar increased use of the ATG7 distal CP site, and previous studies have shown that mice with hematopoietic cells lacking Atg7 develop an MDS-like syndrome.
These data suggest that the S34F mutation alters U2AF1 function in the context of specific RNA sequences, leading to aberrant alternative splicing of target genes, some of which may be relevant for MDS pathogenesis.