Linked Life Data

8652507

Source:http://linkedlifedata.com/resource/pubmed/id/8652507

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
23
pubmed:dateCreated
1996-7-29
pubmed:abstractText
We present the first description of KmDNA, KdDNA, Kcat, and Kmethylation for a mammalian DNA methyltransferase. Homogeneous, 190 000 MTDNA (cytosine-5-)-methyltransferase isolated from mouse erythroleukemia cells has turnover constants of 0.15-0.59 h-1 with single-stranded and unmethylated double-stranded oligonucleotides containing a single CpG dinucleotide. These substrates were designed to mimic DNA transcriptional cis elements previously reported to have cytosine C-5-methylated regulation. The rate-limiting step for these substrates is the methylation step itself. In contrast, hemimethylated double-stranded substrates show burst kinetics, consistent with a rapid methylation event (3 h-1) followed by a slower step which determines steady-state Kcat. Hemimethylated and unmethylated double-stranded DNA shows similar binding affinities; these results reveal the molecular basis for the enzyme's preference for hemimethylated DNA to be the methyl transfer step. Substrates with multiple recognition sites do not show burst kinetics and have turnover rate constants of 6 h-1. Catalytic turnover for the mammalian enzyme is thus approximately 10-fold slower than that for the related bacterial enzymes. Our combined results show quantitatively that one enzyme is certainly capable of both maintenance and de novo methylation and that maintenance of the genomic methylation pattern is preferred over the de novo establishment of new patterns. Direct comparison of the mammalian enzyme with the bacterial DNA cytosine-C5 methyltransferase, M.SssI, indicates dramatic differences in preferences for single-stranded, double-stranded, and hemimethylated double-stranded substrates. Moreover, the specificity hierarchy shown for the M.SssI is derived from very different changes in K(m) and catalysis than those observed for the mammalian DCMTase. These results demonstrate that the M.SssI, and perhaps other DNA cytosine methyltransferases from bacteria, is functionally dissimilar to the mammalian enzyme.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
11
pubmed:volume
35
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7308-15
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:8652507-Animals, pubmed-meshheading:8652507-Base Composition, pubmed-meshheading:8652507-Base Sequence, pubmed-meshheading:8652507-DNA (Cytosine-5-)-Methyltransferase, pubmed-meshheading:8652507-Dinucleoside Phosphates, pubmed-meshheading:8652507-Kinetics, pubmed-meshheading:8652507-Leukemia, Erythroblastic, Acute, pubmed-meshheading:8652507-Mammals, pubmed-meshheading:8652507-Mice, pubmed-meshheading:8652507-Molecular Sequence Data, pubmed-meshheading:8652507-Oligodeoxyribonucleotides, pubmed-meshheading:8652507-Polydeoxyribonucleotides, pubmed-meshheading:8652507-Regulatory Sequences, Nucleic Acid, pubmed-meshheading:8652507-S-Adenosylmethionine, pubmed-meshheading:8652507-Substrate Specificity, pubmed-meshheading:8652507-Transcription, Genetic, pubmed-meshheading:8652507-Tumor Cells, Cultured
pubmed:year
1996
pubmed:articleTitle
Murine DNA cytosine-C5 methyltransferase: pre-steady- and steady-state kinetic analysis with regulatory DNA sequences.
pubmed:affiliation
Department of Chemistry, University of California, Santa Barbara 93106, USA.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S.