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PCNA clamp facilitates action of DNA cytosine methyltransferase 1 on hemimethylated DNA
Author(s) -
Iida Tetsuo,
Suetake Isao,
Tajima Shoji,
Morioka Hiroshi,
Ohta Satoshi,
Obuse Chikashi,
Tsurimoto Toshiki
Publication year - 2002
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1046/j.1365-2443.2002.00584.x
Subject(s) - proliferating cell nuclear antigen , dna clamp , biology , dna replication , dna methylation , dna methyltransferase , dna polymerase delta , dnmt1 , dna polymerase , microbiology and biotechnology , hmg box , dna , replication factor c , biochemistry , eukaryotic dna replication , methylation , methyltransferase , dna binding protein , reverse transcriptase , gene expression , transcription factor , gene , polymerase chain reaction
Background: Proliferating cell nuclear antigen (PCNA) is a ring‐shaped protein known as a processivity factor of DNA polymerase δ. In addition to this role, PCNA interacts with a number of other proteins to increase their local concentration at replicated DNA sites. DNA cytosine methyltransferase 1 (Dnmt1), which preserves epigenetic signals by completing the methylation of hemimethylated DNA after DNA replication, has been indicated as one of these PCNA binding proteins by a previous work. However, the molecular mechanisms and functional significance of their association have not yet been studied. Results: Dnmt1 can be readily isolated from nuclear extracts by PCNA affinity chromatography. Studies of the interactions between the two proteins demonstrate that the N‐terminal region of Dnmt1, which contains a typical PCNA binding motif, has core PCNA binding activity, and that the remaining portion of the protein exerts a negative influence on the interaction of Dnmt1 with PCNA. The affinity of Dnmt1 for DNA is much higher for DNA bound by PCNA than for free DNA. Furthermore, DNA methylation assays with hemimethylated DNA as a substrate revealed that PCNA clamp‐bound DNA is methylated more efficiently by Dnmt1 than is free DNA. Conclusion: These results provide the first biochemical evidence that physical interactions between PCNA and Dnmt1 facilitate the methylation of newly neplicated DNA, on which PCNA remains associated as a functional clamp.