Abstracts (poster) - Wissenschaft Online

Renata Jurkowska, Da Jia, Sergey Ragozin, Nils Ansbach, Claus Urbanke, Xing Zhang,
Richard Reinhardt, Wolfgang Nellen, Xiaodong Cheng, Albert Jeltsch
Multimerisation of the Dnmt3L-Dnmt3a complex on DNA and
its mechanistic implications
DNA methyltransferase 3a (Dnmt3a) and its regulatory factor, DNA methyltransferase 3like
protein (Dnmt3L), are both required for de novo DNA methylation of imprinted
genes in mammalian germ cells, though the basis for imprinting-associated methylation
is not yet clear. X-ray structure analysis shows that the C-terminal domain of Dnmt3L
interacts with the catalytic domain of Dnmt3a. The Dnmt3a-C/Dnmt3L-C complex further
dimerizes through Dnmt3a-3a interaction, forming a tetrameric complex with two active
sites. Substitution of key noncatalytic residues in the Dnmt3a-3L interface or Dnmt3a-3a
interface eliminated enzymatic activity of Dnmt3a and reduced its cofactor and DNA
binding ability, indicating the requirement of the intact interfaces for the function of the
enzyme. Biochemical data show that Dnmt3a-C binds strongly to DNA and forms an
oligomeric, nucleoprotein filament in a very cooperative reaction. We further visualised
the Dnmt3a (and Dnmt3a/Dnmt3L) – DNA filaments using scanning force microscopy
and demonstrated that the multimerization of Dnmt3a is required for its localization to
pericetromeric heterochromatin.
Molecular modeling of a DNA-Dnmt3a dimer suggested that the two active sites are
separated by approximately one DNA helical turn. A periodicity in the activity of Dnmt3a
on long DNA revealed a correlation of methylated CpG sites at distances of 8-10 base
pairs, suggesting that oligomerization leads Dnmt3a to methylate in a periodic pattern. A
similar periodicity of 9.5 base pairs is observed for the frequency of CpG sites in the
differentally-methylated regions of 12 maternally-imprinted mouse genes. These results
suggest a basis for the recognition of differentially-methylated regions in imprinted
genes, involving detection of both nucleosome modification and CpG spacing.
Literature
Jia D*, Jurkowska RZ*, Zhang X, Jeltsch A, Cheng X. A. Structure of Dnmt3a bound to
Dnmt3L suggests a model for de novo DNA methylation. (2007) Nature 449(7159):248-
51.
Jurkowska RZ, Ragozin S, Ansbach N, Urbanke C, Jia D, Reinhard R, Nellen W, Xiaodong
C, Jeltsch A Formation of nucleoprotein filaments by mammalian DNA methyltransferase
Dnmt3a and its complex with regulator Dnmt3L. (2008) Manuscript in preparation.
contact:
Renata Jurkowska
Jacobs University Bremen
Department of Biochemistry
r.jurkowska@jacobs-university.de
Campus Ring 1
28759 Bremen (Germany)
additional information
Renata Jurkowska, Sergey Ragozin and Albet Jeltsch: Biochemistry Lab, School of Engineering and
Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
Nils Ansbach and Wolfgang Nellen: Abt. Genetik, CINSaT, Universität Kassel, Heinrich-Plett-Str. 40,
34132 Kassel, Germany
Claus Urbanke: Medizinische Hochschule, Abteilung Strukturanalyse OE 8830, Carl Neuberg Str. 1,
30625 Hannover, Germany
Da Jia, Xing Zhang and Xiaodong Cheng: Department of Biochemistry, Emory University School of
Medicine, 1510 Clifton Road, Atlanta, GA 30033, USA
Richard Reinhard: Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, D-14195 Berlin-
Dahlem, Germany