Journal Article

Helix–hairpin–helix protein MJ1434 from Methanocaldococcus jannaschii and EndoIV homologue TTC0482 from Thermus thermophilus HB27 do not process DNA uracil residues

Lars Schomacher, Sabine Smolorz, Elena Ciirdaeva, Svetlana Ber, Wilfried Kramer and Hans-Joachim Fritz

in Nucleic Acids Research

Volume 38, issue 15, pages 5119-5129
Published in print August 2010 | ISSN: 0305-1048
Published online April 2010 | e-ISSN: 1362-4962 | DOI: https://dx.doi.org/10.1093/nar/gkq270

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The mutagenic threat of hydrolytic DNA cytosine deamination is met mostly by uracil DNA glycosylases (UDG) initiating base excision repair. However, several sequenced genomes of archaeal organisms are devoid of genes coding for homologues of the otherwise ubiquitous UDG superfamily of proteins. Previously, two possible solutions to this problem were offered by (i) a report of a newly discovered family of uracil DNA glycosylases exemplified by MJ1434, a protein found in the hyperthermophilic archaeon Methanocaldococcus jannaschii, and (ii) the description of TTC0482, an EndoIV homologue from the hyperthermophilic bacterium Thermus thermophilus HB27, as being able to excise uracil from DNA. Sequence homologues of both proteins can be found throughout the archaeal domain of life. Three proteins orthologous to MJ1434 and the family founder itself were tested for but failed to exhibit DNA uracil glycosylase activity when produced in an Ung-deficient Escherichia coli host. Likewise, no DNA uracil processing activity could be detected to be associated with TTC0482, while the protein was fully active as an AP endonuclease. We propose that the uracil processing activities formerly found were due to contaminations with Ung enzyme. Use of Δung-strains as hosts for production of putatively DNA-U processing enzymes provides a simple safeguard.

Journal Article.  6536 words.  Illustrated.

Subjects: Chemistry ; Biochemistry ; Bioinformatics and Computational Biology ; Genetics and Genomics ; Molecular and Cell Biology