Targeting of transcription factor binding sites of SNAI-2 and TCF4 interrupted by the HDAC5 variant showed a significant impact of TCF4 on promoter activity of mutated HDAC5. Our findings contribute not only to the identification of unrecognized genetic causes of familial CRC but also underline the importance of 5’UTR variants affecting transcriptional regulation and the pathogenesis of complex disorders. The gene discussed is TCF4; the disease is colorectal carcinoma.