Cell Nucleus

Methylated sites promote gene
inactivation by de-acetylating
histones:
1. Methylated GC islands (in the proximal promoter)
recruit the binding of the protein MeCP2
2. MeCP2 in-turn recruits 3. Sin3 co-repressor is a
histone de-acetylase (HDAC)
4. which acts by maintaining chromatin condensation,
inaccessible to RNA polymerase.
Note, the big question here is how the cell accomplishes the methylation
in the first place and how it recognizes which genes are to be
inactivated. Largely still an open question.
Also note, in this case the DNA itself is methylated. The histones can be
acetylated, as discussed, and they can be methylated too, which we
didn’t discuss much.
Thursday, January 21, 2010
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