CDX2 is a homeodomain-containing protein, which regulates cellular development in the intestines. The protein has been implicated to play a role in colorectal cancer, showing impaired expression or function in affected individuals (Kim et al., 2004; Da Costa et al., 1999). Ultimately, the protein functions as a tumour suppressor in the intestines, where it inhibits the proliferation of intestinal epithelial cells by up-regulating the expression of cell cycle arrestors in the presence of DNA damage (Saad et al., 2011). An interesting feature of CDX2 is that despite being a monomeric transcription factor, it displays multiple specificity — binding to two consensus sequences with approximately equal affinity. These sequences, namely GCAATAAA and GTCGTAAA, differ only in the three nucleotides in bold. The 3D structure shown was elucidated by Morgunova and colleagues (2018) and shows CDX2 bound to its CAA consensus sequence, emphasising the key interactions that take place at the major and minor grooves.
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