CTCF Complex: Structure and Function

3D Model

CCCTC-binding factor (CTCF) is a complex of human DNA and 11 Zinc Fingers (ZnFs).

It is a transcriptional regulator, activating/binding to methylated cytosine which modulates the organisation of chromatin, converting it to heterochromatin. The CTCF complex is a transcriptional repressor, as heterochromatin is the inactive state of DNA.

The two invariant cytosines on the DNA sequence are in bp locations 2 and 12 (for the DNA strand of ZnF2-7). The ZnFs bind to the DNA in three places each, forming multiple hydrogen bonds with three bordering nucleotides in the DNA sequence. There are no nucleotides in the sequence without a bonded ZnF.

CTCF is highly adaptable, as both the DNA sequence and ZnF consensus sequences can vary highly. Through a combination of hydrogen-bonding, water-mediated H-bonding and van der Waal forces, the ZnFs can consistently bond to the DNA.