Nucleic Acids Research, Vol 27, Issue 8 1795-1801, Copyright © 1999 by Oxford University Press
R Kooistra, JB Zonneveld, AJ Watson, GP Margison, PH Lohman and A Pastink
The protein O 6-alkylguanine-DNA alkyltransferase(alkyltransferase) is
involved in the repair of O 6-alkylguanine and O 4-alkylthymine in DNA and
plays an important role in most organisms in attenuating the cytotoxic and
mutagenic effects of certain classes of alkylating agents. A genomic clone
encompassing the Drosophila melanogaster alkyltransferase gene ( DmAGT )
was identified on the basis of sequence homology with corresponding genes
in Saccharomyces cerevisiae and man. The DmAGT gene is located at position
84A on the third chromosome. The nucleotide sequence of DmAGT cDNA revealed
an open reading frame encoding 194 amino acids. The MNNG-hypersensitive
phenotype of alkyltransferase-deficient bacteria was rescued by expression
of the DmAGT cDNA. Furthermore, alkyltransferase activity was identified in
crude extracts of Escherichia coli harbouring DmAGT cDNA and this activity
was inhibited by preincubation of the extract with an oligonucleotide
containing a single O6-methylguanine lesion. Similar to E.coli Ogt and
yeast alkyltransferase but in contrast to the human alkyltransferase, the
Drosophila alkyltransferase is resistant to inactivation by O
6-benzylguanine. In an E.coli lac Z reversion assay, expression of DmAGT
efficiently suppressed MNNG-induced G:C-->A:T as well as A:T-->G:C
transition mutations in vivo. These results demonstrate the presence of an
alkyltransferase specific for the repair of O 6-methylguanine and O
4-methylthymine in Drosophila.
ARTICLES
Identification and characterisation of the Drosophila melanogaster O6- alkylguanine-DNA alkyltransferase cDNA
MGC Department of Radiation Genetics and Chemical Mutagenesis, Leiden University Medical Centre, Wassenaarseweg 72, 2333 AL Leiden, The Netherlands.
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