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Biochemical characterization of uracil processing activities in the hyperthermophilic archaeon Pyrobaculum aerophilum.


Sartori, A A; Schär, P; Fitz-Gibbon, S; Miller, J H; Jiricny, J (2001). Biochemical characterization of uracil processing activities in the hyperthermophilic archaeon Pyrobaculum aerophilum. Journal of Biological Chemistry, 276(32):29979-29986.

Abstract

Deamination of cytosine to uracil and 5-methylcytosine to thymine represents a major mutagenic threat particularly at high temperatures. In double-stranded DNA, these spontaneous hydrolytic reactions give rise to G.U and G.T mispairs, respectively, that must be restored to G.C pairs prior to the next round of DNA replication; if left unrepaired, 50% of progeny DNA would acquire G.C --> A.T transition mutations. The genome of the hyperthermophilic archaeon Pyrobaculum aerophilum has been recently shown to encode a protein, Pa-MIG, a member of the endonuclease III family, capable of processing both G.U and G.T mispairs. We now show that this latter activity is undetectable in crude extracts of P. aerophilum. However, uracil residues in G.U mispairs, in A.U pairs, and in single-stranded DNA were efficiently removed in these extracts. These activities were assigned to a approximately 22-kDa polypeptide named Pa-UDG (P. aerophilum uracil-DNA glycosylase). The recombinant Pa-UDG protein is highly thermostable and displays a considerable degree of homology to the recently described uracil-DNA glycosylases from Archaeoglobus fulgidus and Thermotoga maritima. Interestingly, neither Pa-MIG nor Pa-UDG was inhibited by UGI, a generic inhibitor of the UNG family of uracil glycosylases. Yet a small fraction of the total uracil processing activity present in crude extracts of P. aerophilum was inhibited by this peptide. This implies that the hyperthermophilic archaeon possesses at least a three-pronged defense against the mutagenic threat of hydrolytic deamination of cytosines in its genomic DNA.

Deamination of cytosine to uracil and 5-methylcytosine to thymine represents a major mutagenic threat particularly at high temperatures. In double-stranded DNA, these spontaneous hydrolytic reactions give rise to G.U and G.T mispairs, respectively, that must be restored to G.C pairs prior to the next round of DNA replication; if left unrepaired, 50% of progeny DNA would acquire G.C --> A.T transition mutations. The genome of the hyperthermophilic archaeon Pyrobaculum aerophilum has been recently shown to encode a protein, Pa-MIG, a member of the endonuclease III family, capable of processing both G.U and G.T mispairs. We now show that this latter activity is undetectable in crude extracts of P. aerophilum. However, uracil residues in G.U mispairs, in A.U pairs, and in single-stranded DNA were efficiently removed in these extracts. These activities were assigned to a approximately 22-kDa polypeptide named Pa-UDG (P. aerophilum uracil-DNA glycosylase). The recombinant Pa-UDG protein is highly thermostable and displays a considerable degree of homology to the recently described uracil-DNA glycosylases from Archaeoglobus fulgidus and Thermotoga maritima. Interestingly, neither Pa-MIG nor Pa-UDG was inhibited by UGI, a generic inhibitor of the UNG family of uracil glycosylases. Yet a small fraction of the total uracil processing activity present in crude extracts of P. aerophilum was inhibited by this peptide. This implies that the hyperthermophilic archaeon possesses at least a three-pronged defense against the mutagenic threat of hydrolytic deamination of cytosines in its genomic DNA.

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Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Molecular Cancer Research
07 Faculty of Science > Institute of Molecular Cancer Research
Dewey Decimal Classification:570 Life sciences; biology
Language:English
Date:2001
Deposited On:09 Jul 2010 12:54
Last Modified:05 Apr 2016 14:09
Publisher:American Society for Biochemistry and Molecular Biology
ISSN:0021-9258
Additional Information:This research was originally published in: Sartori, A A; Schär, P; Fitz-Gibbon, S; Miller, J H; Jiricny, J (2001). Biochemical characterization of uracil processing activities in the hyperthermophilic archaeon Pyrobaculum aerophilum. Journal of Biological Chemistry, 276(32):29979-29986. © the American Society for Biochemistry and Molecular Biology.
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:10.1074/jbc.M102985200
PubMed ID:11399761
Permanent URL: http://doi.org/10.5167/uzh-34472

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