Submitted November 23, 2005
Accepted May 15, 2006
MBD2 is a critical component of a methylcytosine binding
protein complex isolated from primary erythroid cells
Evan P Kransdorf, Shou Zhen Wang, Sheng Zu Zhu, Timothy B Langston, Jeremy W Rupon, and Gordon D Ginder*
Virginia Commonwealth University, Richmond, Virginia, USA
* Corresponding author; email: gdginder{at}hsc.vcu.edu.
The chicken embryonic 
-type globin gene, & [rho],
is a member of a small group of vertebrate genes whose
developmentally regulated expression is mediated by DNA
methylation. Previously, we have shown that a
methylcytosine binding complex binds to the methylated & [rho]-globin gene in vitro. We have now
chromatographically purified and characterized this
complex from adult chicken primary erythroid cells.
Four components of the MeCP1 transcriptional repression
complex were identified: MBD2, RBAP48, HDAC2 and MTA1.
These four proteins, as well as the zinc-finger protein
p66 and the chromatin remodeling factor Mi2, were found
to coelute by gel-filtration analysis and pull-down
assays. We conclude that these six proteins are
components of the MeCPC. In adult erythrocytes,
significant enrichment for MBD2 is seen at the inactive &
[rho]-globin gene by chromatin immunoprecipitation
assay, whereas no enrichment is observed at the active A-globin gene, demonstrating MBD2 binds to the
methylated and transcriptionally silent 
-globin
gene in vivo. Knock-down of MBD2 resulted in
upregulation of a methylated & [rho]-gene contruct in MEL-
& [rho] cells. These results represent the first
purification of a MeCP1-like complex from a primary cell
source and provide support for a role for MBD2 in
developmental gene regulation.
