Transcriptional repression by Drosophila methyl-CpG-binding proteins.
C methylation at genomic CpG dinucleotides has been implicated in the regulation of a number of genetic activities during vertebrate cell differentiation and embryo development. The methylated CpG could induce chromatin condensation through the recruitment of histone deacetylase (HDAC)-containing complexes by methyl-CpG-binding proteins. These proteins consist of the methylated-DNA binding domain (MBD). Unexpectedly, however, several studies have identified MBD-containing proteins encoded by genes of Drosophila melanogaster, an invertebrate species supposed to be void of detectable m(5)CpG. We now report the genomic structure of a Drosophila gene, dMBD2/3, that codes for two MBD-containing, alternatively spliced, and developmentally regulated isoforms of proteins, dMBD2/3 and dMBD2/3Delta. Interestingly, in vitro binding experiments showed that as was the case for vertebrate MBD proteins, dMBD2/3Delta could preferentially recognize m(5)CpG-containing DNA through its MBD. Furthermore, dMBD2/3Delta as well as one of its orthologs in mouse, MBD2b, could function in human cells as a transcriptional corepressor or repressor. The activities of HDACs appeared to be dispensable for transcriptional repression by dMBD2/3Delta. Finally, dMBD2/3Delta also could repress transcription effectively in transfected Drosophila cells. The surprisingly similar structures and characteristics of the MBD proteins as well as DNA cytosine (C-5) methyltransferase-related proteins in Drosophila and vertebrates suggest interesting scenarios for their roles in eukaryotic cellular functions.
Roder
K
K
Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, Taiwan, Republic of China.
Hung
M S
MS
Lee
T L
TL
Lin
T Y
TY
Xiao
H
H
Isobe
K I
KI
Juang
J L
JL
Shen
C J
CJ
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002843:Chromatin / Q000378:metabolism / Q000648:ultrastructure; D018899:CpG Islands; D004247:DNA / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D019143:Evolution, Molecular; D005786:Gene Expression Regulation; D017344:Genes, Insect; D006655:Histone Deacetylases / Q000502:physiology; D006801:Humans; D019476:Insect Proteins / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012097:Repressor Proteins / Q000502:physiology*; D013045:Species Specificity; D014158:Transcription, Genetic
D002843:Chromatin; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D019476:Insect Proteins; C115368:MBD2 protein; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D004247:DNA; D006655:Histone Deacetylases