insulator proteins

Transcriptional insulators are DNA elements that set boundaries on the actions of enhancer and silencer elements and thereby organize the eukaryotic genome into regulatory domains.

All vertebrate insulators appear to use the versatile CTCF protein. CTCF uses various combinations of its 11 zinc fingers to recognize a variety of unrelated DNA sequences. Once bound to DNA, CTCF can function as a transcriptional insulator, repressor, or activator, depending on the context of the binding site.

In normal cells, insulator proteins such as the transcription factor CTCF establish chromatin boundaries, and CTCF is involved in the regulation of imprinting, where it is required to protect against de novo methylation.

Intriguingly, methylation of the CTCF recognition sequence abolishes CTCF binding, indicating that specific DNA methylations may have long-range consequences.

See also

 genomic imprinting
 DNA hypermethylation