title: Characterization of the major formamidopyrimidine-DNA glycosylase homolog in Mycobacterium tuberculosis and its linkage to variable tandem repeats.
abstract: The ability to repair DNA damage is likely to play an important role in the survival of facultative intracellular parasites because they are exposed to high levels of reactive oxygen species and nitrogen intermediates inside phagocytes. Correcting oxidative damage in purines and pyrimidines is the primary function of the enzymes formamidopyrimidine (faPy)-DNA glycosylase (Fpg) and endonuclease VIII (Nei) of the base excision repair pathway, respectively. Four gene homologs, belonging to the fpg/nei family, have been identified in Mycobacterium tuberculosis H37Rv. The recombinant protein encoded by M. tuberculosis Rv2924c, termed Mtb-Fpg1, was overexpressed, purified and biochemically characterized. The enzyme removed faPy and 5-hydroxycytosine lesions, as well as 8-oxo-7,8-dihydroguanine (8oxoG) opposite to C, T and G. Mtb-Fpg1 thus exhibited substrate specificities typical for Fpg enzymes. Although Mtb-fpg1 showed nearly complete nucleotide sequence conservation in 32 M. tuberculosis isolates, the region upstream of Mtb-fpg1 in these strains contained tandem repeat motifs of variable length. A relationship between repeat length and Mtb-fpg1 expression level was demonstrated in M. tuberculosis strains, indicating that an increased length of the tandem repeats positively influenced the expression levels of Mtb-fpg1. This is the first example of such a tandem repeat region of variable length being linked to the expression level of a bacterial gene.
authors.affiliation: Centre for Molecular Biology and Neuroscience, Institute of Microbiology, University of Oslo, Oslo University Hospital (Rikshospitalet), Oslo, Norway.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Olsen
authors.forename: Seetha V
authors.initials: SV
authors.lastname: Balasingham
authors.forename: Tonje
authors.initials: T
authors.lastname: Davidsen
authors.forename: Ephrem
authors.initials: E
authors.lastname: Debebe
authors.forename: Einar A
authors.initials: EA
authors.lastname: Rødland
authors.forename: Dick
authors.initials: D
authors.lastname: van Soolingen
authors.forename: Kristin
authors.initials: K
authors.lastname: Kremer
authors.forename: Ingrun
authors.initials: I
authors.lastname: Alseth
authors.forename: Tone
authors.initials: T
authors.lastname: Tønjum
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017124:Conserved Sequence; D004260:DNA Repair; D004269:DNA, Bacterial / Q000378:metabolism*; D043382:DNA-Formamidopyrimidine Glycosylase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D018598:Minisatellite Repeats; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D017385:Sequence Homology; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D043382:DNA-Formamidopyrimidine Glycosylase