Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

06-Methylguanine-DNA methyltransferase (MGMT) is present in various organisms, from bacteria to human cells, and plays an important role in preventing mutations caused by alkylating substances. To understand better the regulatory mechanism involved in the expression of the gene and to construct a mouse model to investigate roles of the enzyme in carcinogenesis, the genomic sequence for mouse methyltransferase was isolated and characterized. The gene consists of 5 exons and spans over 180 kb, whereas mRNA for the enzyme was less than 1 kb. The promoter region for the gene is GC-rich, contains many Sp1 recognition sequences and lacks typical TATA and CCAAT boxes. Primer extension and S1 mapping revealed the existence of multiple transcription initiation sites, among which a major site was defined as +1. The putative promoter region was placed upstream of the chloramphenicol acetyltransferase (CAT) reporter gene and the construct was introduced into mouse NIH-3T3 cells. Deletion analyses revealed that a sequence from -262 to + 56 carries the basic promoter activity. In addition, an adjacent region, spanning from +56 to +95, carries an E2F-like element that greatly stimulates the frequency of transcription. Alteration of TTTTGGGGC to TTAACGGGC considerably reduced the activity.
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PMID:Organization and expression of the mouse gene for DNA repair methyltransferase. 889 58

O6-Methylguanine-DNA methyltransferase (MGMT), an enzyme that repairs adducts at O6 of guanine in DNA, is a major determinant of susceptibility to simple methylating carcinogens or of tumor response to anticancer chloroethylating drugs. To investigate the mechanisms underlying cellular expression of this DNA repair enzyme, we focused on the role of a 59-bp enhancer of the human MGMT gene in the regulation of its expression. By using chloramphenicol acetyltransferase reporter assays, we found that the enhancer activity, which was present in both MGMT-expressing (Mer+) and -deficient (Mer-) cells, correlated with the endogenous MGMT activity in Mer+ cell lines. Band-shift assays and deletion analysis of the 59-bp sequence defined a minimal 9-mer cis element (5'-CTGGGTCGC-3') for specific trans factor binding. The MGMT enhancer binding protein (MEBP), 45 kDa by Southwestern blot analysis, was present in the nuclei of all Mer+ cells tested but was apparently restricted to the cytoplasm of Mer- cells. We conclude that the MEBP-enhancer interaction plays an important role in regulating constitutive MGMT expression in Mer+ cells and that MEBP exclusion from the nucleus may account for the down-regulation of MGMT in Mer- cells.
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PMID:Cytoplasmic sequestration of an O6-methylguanine-DNA methyltransferase enhancer binding protein in DNA repair-deficient human cells. 911 92