The Unique Pairing of a Ubiquitous and a Male Germ Cell Specific
Factor with the same 11 Zn-finger Domain Encoded by Two
Paralagous Genes: CTCF at 16q22 and BORIS at 20q13are involved
in Epigenetics of Normal biology and Cancer  Victor Lobanenkov
CTCF has been discovered as the first example of a true
"multivalent" nuclear factor capable of specific recognition of
varying -50-bp-long DNA sites with no single "consensus"
sequence that could describe all of the binding sites [reviewed
in (1)]. The ubiquitously expressed gene is conserved from
Drosophila through the mammalian radiation showing, within the
11 Zn-finger DNA-binding domain, - 100% amino acid identity in
all vertebrates. Remarkably, chicken CTCF can bind to all
Drosophila DNA sequences identified as targets for Drosophila
CTCF, but Drosophila CTCF cannot bind to all vertebrate CTCF
targets. This suggests that during evolution, CTCF was co-opted
to serve an increasing number of functions. In mammals, these
functions have apparently converged because