Cytosine methylation transforms an E2F site in the retinoblastoma gene promoter into a binding site for the general repressor methylcytosine-binding protein 2 (MeCP2).
The CpG-rich promoter of the retinoblastoma tumor suppressor gene (Rb-1) is normally unmethylated. However, aberrant methylation of CpG dinucleotides within the Rb-1 promoter has been depicted in certain tumors, which determines transcriptional inactivity of the gene and absence of the pRb retinoblastoma protein. Here we have concentrated on an E2F-binding site in the Rb-1 promoter. We show that the E2F site is required for cell-cycle regulated Rb-1 transcription in non-transformed cells. The function of the E2F site is associated with its ability to interact with several activating factors of the E2F family. In contrast, in vitro methylation of two tandemly arranged CpGs in the E2F recognition site prevents binding by E2F factors, and determines instead the recruitment of the general repressor methylcytosine-binding protein 2 (MeCP2). These results suggest that the interaction of MeCP2 with the methylated version of the E2F site may represent a step towards Rb-1 promoter inactivity in tumor cells.
Di Fiore
B
B
CNR Centre of Evolutionary Genetics, c/o University 'La Sapienza', Via degli Apuli 4, Rome 00185, Italy.
Palena
A
A
Felsani
A
A
Palitti
F
F
Caruso
M
M
Lavia
P
P
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D018899:CpG Islands / Q000235:genetics; D003596:Cytosine / Q000378:metabolism*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D050684:E2F Transcription Factors; D051783:Methyl-CpG-Binding Protein 2; D051379:Mice; D008957:Models, Genetic; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012097:Repressor Proteins / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D016160:Retinoblastoma Protein / Q000235:genetics*; D056465:Retinoblastoma-Binding Protein 1; D016196:S Phase; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D015854:Up-Regulation
C533431:Arid4a protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; C497393:Mecp2 protein, mouse; D051783:Methyl-CpG-Binding Protein 2; D012097:Repressor Proteins; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D003596:Cytosine; D004247:DNA