Updated project metadata. RNA splicing and the DNA damage response are intriguingly linked in mammals but the underlying mechanisms remain poorly understood. Using an in vivo biotinylation tagging approach in mice we show that XAB2, the human homologue of the yeast pre-mRNA-splicing factor SYF1 has a functional role in Nucleotide Excision Repair (NER) and the DNA damage response (DDR) in mammals. XAB2 interacts with spliceosome factors and is part of the core spliceosome that binds to spliceosomal U4 and U6 snRNAs during hepatic development. Ablation of XAB2 leads to defective NER, intron retention, the aberrant accumulation of pre-mRNAs and to a faulty ATM/ATR DDR signaling. Using functional approaches, we find that XAB2 dissociates from RNA targets upon persistent DNA damage or transcription blockage and from spliceosomal RNAs in the NER-defective developing livers. Thus, XAB2 functionally links NER to the spliceosomal response to DNA damage during hepatic development with important ramifications for transcription-coupled DNA repair disorders.