Splicing factors of the SF3b complex PHF5A and SF3B1 regulate the DNA damage response in ALL

To identify potential regulators of propagation and self-renewal of Acute Lymphoblastic Leukaemia (ALL), we performed a genome-wide RNAi screen that identified the splicing factor PHF5A. PHF5A is a subunit of the SF3b protein complex together with SF3B1, which has also been implicated in several haematological malignancies. We show that PHF5A and SF3B1 knockdown significantly reduces cell proliferation and colony forming ability. Moreover, knockdown of PHF5A and SF3B1 induce DNA strand breaks as indicated by comet assay and increased y-H2AX levels. Using RNA-seq datasets, we validated candidate genes which have been affected by differential splicing and/or differential expression. Notably, PHF5A and SF3B1 knockdown reduced FANCD2 expression and induced skipping of exon 22 associated with impaired mono-ubiquitination of the FANCD2 protein. Furthermore, expression of RAD51, a key DNA repair factor, also decreased upon PHF5A and SF3B1 knockdown. Taken together, our data show that splicing factors regulate the DNA Damage response in ALL.