Mutations in SPOP, the gene most frequently point-mutated in primary prostate cancer, are associated with a high degree of genomic instability and deficiency in homologous recombination repair of DNA but the underlying mechanisms. SPOP knockdown leads to spontaneous replication stress and impaired recovery from replication fork stalling. An SPOP interactome analysis shows that wild type (WT) SPOP but not mutant SPOP associates with multiple proteins involved in transcription, mRNA splicing and export. Consistent with the association of SPOP with transcription, splicing and RNA export complexes, the decreased expression of several components of the DNA damage response pathway occurs at the level of transcription.