The repressor MDBP-2 is a member of the histone H1 family that binds preferentially in vitro and in vivo to methylated nonspecific DNA sequences.
MDBP-2 is a repressor that binds preferentially to methylated DNA. Peptides derived from MDBP-2 were sequenced. The sequences of the two peptides, KPAGPS-VTELITK and ALAAGGYDVEK, are identical to those found in the chicken histone H1 core protein. In SDS/polyacrylamide gels MDBP-2 has an apparent molecular mass of 21 kDa, and antibodies directed against calf thymus total histone H1 cross-react with MDBP-2. The preferential binding of affinity-purified MDBP-2 to methylated DNA is not sequence-specific but requires a minimum length of 30 base pairs and one pair of symmetrically methylated (i.e., methylated on both strands) CpG dinucleotides. As previously shown, there is a decrease in the binding activity of MDBP-2 to methylated DNA upon estradiol treatment. Immunoblots show that upon estradiol treatment the amount of immunocrossreacting MDBP-2 protein remains unchanged. MDBP-2 enables another protein to bind DNA which by itself does not bind methylated DNA. Ultraviolet crosslinking and selective immunoadsorption assays with anti-histone H1 antibodies show that in vivo MDBP-2 preferentially binds to the methylated repressed vitellogenin gene. It is concluded that MDBP-2 may participate in the long-term silencing of genes (formation of heterochromatin) through selective binding to methylated DNA.
Jost
J P
JP
Friedrich Miescher Institute, Basel, Switzerland.
Hofsteenge
J
J
D044503:5-Methylcytosine; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002645:Chickens; D003596:Cytosine / Q000031:analogs & derivatives* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006657:Histones / Q000737:chemistry; D046911:Macromolecular Substances; D008745:Methylation; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D012097:Repressor Proteins / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014819:Vitellogenins / Q000235:genetics
D004268:DNA-Binding Proteins; D006657:Histones; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D012097:Repressor Proteins; D014819:Vitellogenins; D044503:5-Methylcytosine; D003596:Cytosine