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  • Title: Substrate preferences of human placental DNA methyltransferase investigated with synthetic polydeoxynucleotides.
    Author: Carotti D, Palitti F, Mastrantonio S, Rispoli M, Strom R, Amato A, Campagnari F, Whitehead EP.
    Journal: Biochim Biophys Acta; 1986 Mar 26; 866(2-3):135-43. PubMed ID: 3955052.
    Abstract:
    A DNA methyltransferase partly purified from human placenta has been tested on a variety of synthetic polydeoxynucleotides. The results showed that: the enzyme is most active as a 'maintenance' or 'hemi-' methylase but also has some de novo methylating activity; the presence or absence of A or T in the substrate strand has little influence on maintenance or de novo activity, while polymers containing C but not G in the same strand are poor de novo substrates and bind poorly to the enzyme; single-stranded polymers are about as good substrates as double-stranded ones, and the effects of nucleotide composition (particularly G and mC content) on enzyme activity with single strands are similar to those with double-stranded polymers; strands in which all the cytosines are methylated bind the enzyme well. A mechanism is suggested involving two different sites on the enzyme that recognize CG and mCG, and which rationalizes the activity of eukaryotic DNA methyltransferases towards single-stranded DNA.
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