HSF2 Safeguards Against Genomic Instability and Radiation-Induced T-ALL Via Regulation of Pre-mRNA Splicing
Prompt and accurate responses to DNA damage are crucial for maintaining normal cellular homeostasis and avoiding cell death.  These responses involve the activation of DNA repair pathways and changes in gene expression.  RNA polymerase II (RNAPII) is responsible for transcribing protein-coding genes and small nuclear RNAs (snRNAs).  Concurrent with transcription, pre-mRNA undergoes splicing by the spliceosome, a complex consisting of five ribonucleoproteins (snRNPs), snRNAs, and additional factors, which ensures proper pre-mRNA splicing and generation of mature mRNA, thereby promoting proteome diversity.    In this study, we provide new insights into the role of HSF2 in pre-mRNA splicing and maintenance of genomic stability.  We observed a significant reduction in RNAPIICTD pS7 following loss of HSF2 and this is accompanied by the inhibition of RNAPII recruitment to snRNA gene promoters and a significant reduction in snRNA transcription.  Moreover, the observed reduction in snRNAs expression in cells lacking HSF2 is associated with impaired pre-mRNA splicing and several other consequences.  These include a spontaneous increase in DNA damage, enhanced formation of R-loops, and elevated cellular sensitivity to ionizing radiation (IR).  These findings suggest that loss of HSF2 leads to multiple disruptions in cellular processes, ultimately resulting in compromised genome stability and increased susceptibility to DNA damage.    Furthermore, HSF2-deficient mice exhibit an accelerated IR-induced T cell acute lymphoblastic leukemia (T-ALL), as evidenced by the reduced snRNA levels and expression of IR-induced DNA repair genes.  Our findings reveal a previously unrecognized role for HSF2 in the process of snRNA transcription and its loss highlights its pathological consequences.   These features are also mirrored by the loss of the HSF2 target gene, HSP110, suggesting that HSP110 contributes, at least in part, to the phenotypes observed following HSF2 loss. Overall design: Total RNA was isolated from (1) Lin-cKit cells sorted (by FACS) from bone marrow of WT or hsf2-/- mice; (2) parental, sgHsf2, or sgHsp110 K562 cells. The RNA was used for RNA-seq. The gene expression profiles between different genotypes cells were compared and analyzed for differential expression and alternative splicing.