A novel functional role for MMSET in RNA processing based on the link between the REIIBP isoform and its interaction with the SMN complex.

The chromosomal translocation t(4;14) deregulates MMSET (WHSC1/NSD2) expression and is a poor prognostic factor in multiple myeloma (MM). MMSET encodes two major protein isoforms. We have characterized the role of the shorter isoform (REIIBP) in myeloma cells and identified a clear and novel interaction of REIIBP with members of the SMN (survival of motor neuron) complex that directly affects the assembly of the spliceosomal ribonucleic particles. Using RNA-seq we show that REIIBP influences the RNA splicing pattern of the cell. This new discovery provides novel insights into the understanding of MM pathology, and potential new leads for therapeutic targeting.