Dnmt2 Dnmt3a

Viable and normal morphology, 70% decrease in total 5-methylcytosine.

Viable, characteristics not described in detail.

Viable and normal.

Indistinguishable from wild type.

Normal

Normal

Viable and normal undif- Normal and ferentiated morphology. fertile. The de novo methylation activity on proviral DNA was normal. Centromeric-minor satellite DNA repeats were normally methylated.

DNMT3B Viable and normal undif- Normal and ferentiated morphology. fertile. The de novo methylation activity on proviral DNA was normal. Centromeric-minor satellite DNA repeats were substantially demethylated.

DNMT3A Double mutant ES cells Not reported.

and DNMT3B completely lacked de novo methylation activity on proviral DNA. Centro-meric-minor satellite DNA repeats were demethylated to the same level as DNMT3B-\- ES cells.

DNMT3L Viable, characteristics Normal and not described in detail. fertile.

Failed to develop beyond mid-gestation, embryonic lethality.28

Homozygous mutant males showed normal fertility. Homozygous mutant females were infertile. Heterozygous offspring of homozygous females showed demethylation at certain imprinted loci, but not over the whole genome.95

No significant phenotype.16

Appeared normal at birth, showed undergrowth at 18 days and died by 4 weeks of age. Retroviral DNA was methylated at normal levels.26

No viable homozygous mi ce were born. Retroviral DNA was slightly undermethylated.26

Double homozygous embryos showed smaller size at E8.5 and died before E11.5. Retroviral DNA was highly undermethylated.26

Both sexes born normal but sterile. Adult testes had severe hypogonadism. Females showed a maternal-effect lethal in that heterozygous progeny of homozygous females died before midgestation. Maternal methylation imprints were markedly disrupted, while genome-wide methylation patterns were normal.

Table 4. Proteins interacting with mammalian DNA methyltransferases

DNA Methyl-transferase

Interacting Protein

Function of Interacting Protein

Possible Role in Vivo

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