The RNA-binding proteins TIA1 and TIAL1 are required for the expression of the DNA damage repair machinery during B cell lymphopoiesis.

B-cell lymphopoiesis requires dynamic modulation of the B-cell transcriptome at the post-transcriptional level, although the implication of RNA binding proteins (RBPs) remain largely unknown. Here we show that the RBPs TIA1 and TIAL1 are essential in B cells and, if deleted, there is a developmental block at the pro-B cell stage. TIA1 and TIAL1 have redundant functions. They act together as global splicing regulators for the expression of mRNAs including those involved in DNA damage repair in pro-B cells. Mechanistically, TIA1 and TIAL1 bind to 5'splice sites for exon definition, splicing and expression of DNA damage sensors like Chek2 and Rif1. In their absence, pro-B cells show exacerbated DNA damage, altered P53 expression and increased cell death. Altogether, our study uncovers the importance of tight regulation of mRNA splicing by TIA1 and TIAL1 for the expression of integrative transcriptional programs for DNA damage sensing and repair during B-cell development. Overall design: Pro B cells were expanded from total bone marrow of C57BL/6 mice in cell stroma-free cultures in the presence of recombinant mouse IL7.