THO/TREX is a conserved complex with a role in messenger ribonucleoprotein biogenesis that links gene expression and genome instability. Here we show that human THO interacts with MFAP1, a spliceosome-associated factor. Interestingly, MFAP1 depletion impairs cell proliferation and genome integrity, increasing ?H2AX foci and DNA breaks. This phenotype is not dependent either on transcription or RNA-DNA hybrids. Mutations in the yeast orthologous gene SPP381, also confer a similar transcription-independent genome instability supporting a conserved role. MFAP1 depletion has a wide effect on splicing and gene expression in human cells, determined by transcriptome analyses, that affects a number of DNA damage response (DDR) genes, which supports an indirect role of MFAP1 on genome integrity. Our work defines a novel functional interaction between THO and RNA processing and argues that splicing factors may contribute to genome integrity indirectly by regulating the expression of DDR genes rather than by a direct role. Overall design: Analysis of gene expression in the Saccharomyces cerevisiae mutant spp381-ts under 1h of restrictive temperature.