Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.5.1.2 (DNA ligase)
 2,749 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We described previously the isolation of a Saccharomyces cerevisiae 3-methyladenine (3-MeAde) DNA glycosylase repair gene (MAG) by its expression in glycosylase-deficient Escherichia coli alkA tag mutant cells and its ability to rescue these cells from the toxic effects of alkylating agents. Here we extend this cross-species functional complementation approach to the isolation of a full-length human 3-MeAde DNA glycosylase cDNA that rescues alkA tag E. coli from killing by methyl methanesulfonate, and we have mapped the gene to human chromosome 16. The cloned cDNA, expressed from the pBR322 beta-lactamase promoter, contains an 894-base-pair open reading frame encoding a 32,894-Da protein able to release 3-MeAde, but not 7-methylguanine, from alkylated DNA. Surprisingly, the predicted human protein does not share significant amino acid sequence homology with the bacterial AlkA and Tag glycosylases or the yeast MAG glycosylase, but it does share extensive amino acid sequence homology with a rat 3-MeAde DNA glycosylase and significant DNA sequence homology with genes from several mammalian species. The cloning of a human 3-MeAde DNA glycosylase cDNA represents a key step in generating 3-MeAde repair-deficient cells and the determination of the in vivo role of this DNA repair enzyme in protecting against the toxic and carcinogenic effects of alkylating agents.
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PMID:Cloning and characterization of a 3-methyladenine DNA glycosylase cDNA from human cells whose gene maps to chromosome 16. 192 75

Short single-stranded gaps in circular DNA molecules can be generated enzymatically, often at predetermined sites. These can serve as targets for in vitro mutagenesis procedures that result in alterations in nucleotide sequence within or very near the gap. Deamination of unpaired cytosine residues with sodium bisulfite has been used to induce mutations in the BglI restriction site of SV40 DNA and within defined regions of the beta-lactamase gene on pBR322. A new method of induction of mutations at gaps, called "gap misrepair," has been developed; it was used to cause changes at the HindIII and C1aI restriction sites on pBR322 DNA. Gap misrepair reactions using DNA polymerase I of Micrococcus luteus in the presence of T4 DNA ligase and three of the four deoxynucleoside triphosphates yielded all three possible substitutions for adenine and cytosine residues in the DNA.
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PMID:Single-stranded gaps as localized targets for in vitro mutagenesis. 628 91

Here, we describe assembly PCR as a method for the synthesis of long DNA sequences from large numbers of oligodeoxyribonucleotides (oligos). The method, which is derived from DNA shuffling [Stemmer, Nature 370 (1994a) 389-391], does not rely on DNA ligase but instead relies on DNA polymerase to build increasingly longer DNA fragments during the assembly process. A 1.1-kb fragment containing the TEM-1 beta-lactamase-encoding gene (bla) was assembled in a single reaction from a total of 56 oligos, each 40 nucleotides (nt) in length. The synthetic gene was PCR amplified and cloned in a vector containing the tetracycline-resistance gene (TcR) as the sole selectable marker. Without relying on ampicillin (Ap) selection, 76% of the TcR colonies were ApR, making this approach a general method for the rapid and cost-effective synthesis of any gene. We tested the range of assembly PCR by synthesizing, in a single reaction vessel containing 134 oligos, a high-molecular-mass multimeric form of a 2.7-kb plasmid containing the bla gene, the alpha-fragment of the lacZ gene and the pUC origin of replication. Digestion with a unique restriction enzyme, followed by ligation and transformation in Escherichia coli, yielded the correct plasmid. Assembly PCR is well suited for several in vitro mutagenesis strategies.
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PMID:Single-step assembly of a gene and entire plasmid from large numbers of oligodeoxyribonucleotides. 759 Mar 20