Table 1.
Methylation-Sensitive and -Dependent DNA-Binding Proteins and their Putative Functions
| DNA-binding factor | Effect of methylation of target sequence (binding) | Factor mol. weight | Target sequence | Comments | Reference |
| Myc/Myn CREB/ATF NFKB AP-2 MLTF/USF EBP-80 VBP1 | inhibits | N.A. | N.A. | a selection of general transcription factors with binding inhibited by methylation | Tate and Bird (1993) |
| Xistpromoter BP1 | inhibits | unknown | GCGCCGCGG | putative factor that binds unmethylated sequence upstream of Xisttranscription start site and has a positive effect on expression (seeXist promoter BP2 below) | Huntriss et al. (1997) |
| AP-1 | permits | N.A. | TGACTCG | methylation of the X-sequence in the first exon of the metastasisassociated gene mts-1 induces Fos/Jun binding resulting in transcriptional silencing | Tulchinsky et al. (1996) |
| MMBP-1 MMBP-2 MMBP-3 | permits permits permits | 42 kD 63 kD 50–60 kD | CACGTG | three factors isolated from C2C12 cells that bind the methylated form of the c-Myc binding site (expressed only in actively proliferating cells) | Suetake et al. (1993/95) |
| DBPm | permits | 50 kD | 35-mer (see Ref.) | isolated from pea seed. Plant methylation plays roles in transposable element silencing and general control of development and flowering | Ehrlich et al. (1993) |
| Xistpromoter BP2 | permits | 100 kD | GCGCCGCGG | when methylated the target sequence binds this transcriptional silencer, replacing (outcompeting?) the Xist promoter BP1 described above | Huntriss et al. (1997) |
| HMBP | permits | 300-kD complex | 43-mer (see Ref.) | methylation of 3 SP1-like sites in the 5′ LTR of HIV can lower expression of the viral-encoded genes (role in AIDS latency?); HMBP, expressed in T lymphocytes, is thought to participate in this inhibition as it only binds the methylated target site | Joel et al. (1993) |
| RFX1, 2, and 3 | permits | 2 × 105-kD complex | GCCGTCATGGCGCC | (also known as EF-C, MDBP, NF-X, etc), family of 5 + conserved DNA binding proteins. Involved in MHCII and viral gene expression. RFX1, 2, and 3 shown toprefer some target siteswhen methylated; transcriptional activators | Zhang et al. (1993) Emery et al. (1996) |
| MDBP-2-H1 | permits | 47 kD | methylated DNA | member of the histone H1 family found in avian liver; preference for association with methylated DNA; shown to be truncated form of normal H1; general significance unknown | Schwarz et al. (1977) |
| MeCP1 | permits | 400/800 kD | several methyl-CpGs | PCM1 (36/80 kD) is a constituent of this large complex | Cross et al. (1997) |
| MeCP2 | permits | 80 kD | 2 methyl-CpGs | abundant butinsufficient in quantityto bind to all genome’smethylated CpGs | Nan et al. (1997) |
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Modified from Tate and Bird (1993).
