The minimal repression domain of MBD2b overlaps with the methyl-CpG-binding domain and binds directly to Sin3A

Different mechanisms mediating methylation-dependent repression have been d emonstrated. Two of these mechanisms play a role in the context of the gran ulocyte/macrophage-specific lysozyme gene: direct interference with DNA bin ding of the transcription factor GA-binding protein and deacetylation of hi stones. Besides enhancement in the unmethylated state, and transcriptional repression upon DNA methylation, the lysozyme downstream enhancer confers t issue-specific demethylation, Because both demethylation activity and repre ssion ability have been attributed to the methyl-CpG-binding domain-contain ing protein MBD2, we analyzed this protein. The short form MBD2b binds to t he methylated lysozyme enhancer and mediates transcriptional repression. MB D2b is capable of binding to the transcriptional repressor Sin3A The intera ction domain of Sin3A required for binding to MBD2b contains the paired amp hipathic helix 3, We identified a minimal functional domain that confers bo th transcriptional repression as well as the interaction to Sin3A in contra st to the functionally related proteins MeCP2 and MBD1, the repression doma in of MBD2b overlaps with the methyl-CpG-binding domain.