PRMT5 genomic deregulation supports growth and stress tolerance in chronic lymphocytic leukemia

Patients suffering from chronic lymphocytic leukemia (CLL) display highly diverse clinical courses ranging from indolent cases to aggressive disease with genetic and epigenetic features resembling this diversity. Here, we developed a comprehensive approach combining a variety of molecular and clinical data to identify translocation events disrupting long-range chromatin interactions and causing cancer-relevant transcriptional deregulation. Thereby, we identified a B cell specific cis-regulatory element restricting the expression of genes in the associated locus, including PRMT5 and DAD1, two factors with oncogenic potential. Examining the role of PRMT5 in CLL identified transcriptional programs associated with pathways of stress tolerance and growth support, maintaining MYC-driven gene expression in vivo and in vitro. Conversely, inhibition of PRMT5 impairs factors involved in DNA-repair and sensitizes cells for apoptosis. Finally, we show that artificial deletion of the regulatory element from its endogenous context resulted in upregulation of corresponding genes, including PRMT5. Furthermore, such disruption renders PRMT5 transcription vulnerable to additional stimuli and subsequently also alters the expression of downstream PRMT5 targets.