The Drosophila MBD2/3 protein mediates interactions between the MI-2 chromatin complex and CpT/A-methylated DNA.
Methyl-DNA binding proteins play an important role in epigenetic gene regulation. The Drosophila genome encodes a single protein (MBD2/3) with extended homologies to the vertebrate methyl-DNA binding proteins MBD2 and MBD3. However, very little is known about its functional properties. We have now characterized an MBD2/3 null mutant allele that is viable and fertile. This mutation caused a strong dominant suppression of position-effect variegation and also resulted in a high rate of chromosome segregation defects during early embryogenesis. Confocal analysis of mutant embryos showed local displacement of MI-2 from DNA and indicated that MBD2/3 is associated with only a subset of MI-2 complexes. In addition, band shift experiments demonstrated a specific binding of MBD2/3 to CpT/A-methylated DNA, which reflects the endogenous DNA methylation pattern of Drosophila. Consistently, the localization of MBD2/3 was disrupted in embryos with reduced levels of DNA methylation. Our data provide novel insights into the function of MBD2/3 proteins and strongly suggest the existence of methylation-dependent chromatin structures in Drosophila.
Marhold
Joachim
J
Research Group Epigenetics, Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 580, 69120 Heidelberg, Germany.
Kramer
Katja
K
Kremmer
Elisabeth
E
Lyko
Frank
F
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D001324:Autoantigens / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004330:Drosophila / Q000196:embryology / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D011485:Protein Binding; D020798:Two-Hybrid System Techniques
D001324:Autoantigens; D002843:Chromatin; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C116095:Mi-2 protein, Drosophila; D049452:Green Fluorescent Proteins; D000251:Adenosine Triphosphatases