From Proteopediaproteopedia link
Crystal structure of mouse DNMT1(650-1602) in complex with DNA
[DNMT1_MOUSE] Methylates CpG residues. Preferentially methylates hemimethylated DNA. Associates with DNA replication sites in S phase maintaining the methylation pattern in the newly synthesized strand, that is essential for epigenetic inheritance. Associates with chromatin during G2 and M phases to maintain DNA methylation independently of replication. It is responsible for maintaining methylation patterns established in development. DNA methylation is coordinated with methylation of histones. Mediates transcriptional repression by direct binding to HDAC2. In association with DNMT3B and via the recruitment of CTCFL/BORIS, involved in activation of BAG1 gene expression by modulating dimethylation of promoter histone H3 at H3K4 and H3K9.  
Publication Abstract from PubMed
Maintenance of genomic methylation patterns is mediated primarily by DNA methyltransferase-1 (DNMT1). We have solved structures of mouse DNMT1 composed of CXXC, tandem bromo-adjacent homology (BAH1/2) and methyltransferase domains bound to DNA containing unmethylated CpG sites. The CXXC specifically binds to unmethylated CpG dinucleotide and positions the CXXC-BAH1 linker between the DNA and the active site of DNMT1, thereby preventing de novo methylation. In addition, a loop projecting from BAH2 interacts with the target recognition domain (TRD) of the methyltransferase, stabilizing the TRD in a retracted position, and preventing it from inserting into the DNA major groove. Our studies identify an autoinhibitory mechanism, whereby occlusion of unmethylated CpG dinucleotides from de novo methylation ensures that only hemimethylated CpG dinucleotides gain access to the active site.
Structure of DNMT1-DNA Complex Reveals a Role for Autoinhibition in Maintenance DNA Methylation.,Song J, Rechkoblit O, Bestor TH, Patel DJ Science. 2010 Dec 16. PMID:21163962
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.