Mutations in the CCGTTCACA DnaA box of Mycobacterium tuberculosis oriC that abolish replication of oriC plasmids are tolerated on the chromosome.
The origin of replication (oriC) region in some clinical strains of Mycobacterium tuberculosis is a hot spot for IS6110 elements. To understand how clinical strains with insertions in oriC can replicate their DNA, we characterized the oriC regions of some clinical strains. Using a plasmid-based oriC-dependent replication assay, we showed that IS6110 insertions that disrupted the DnaA box sequence CCGTTCACA abolished oriC activity in M. tuberculosis. Furthermore, by using a surface plasmon resonance technique we showed that purified M. tuberculosis DnaA protein binds native but not mutant DnaA box sequence, suggesting that stable interactions of the DnaA protein with the CCGTTCACA DnaA box are crucial for replication of oriC plasmids in vivo. Replacement by homologous recombination of the CCGTTCACA DnaA box sequence of the laboratory strain M. tuberculosis H37Ra with a mutant sequence did not result in nonviability. Together, these results suggest that M. tuberculosis strains have evolved mechanisms to tolerate mutations in the oriC region and that functional requirements for M. tuberculosis oriC replication are different for chromosomes and plasmids.
Dziadek
Jaroslaw
J
Department of Biochemistry, The University of Texas Health Center at Tyler, 75708-3154, USA.
Rajagopalan
Malini
M
Parish
Tanya
T
Kurepina
Natalia
N
Greendyke
Rebecca
R
Kreiswirth
Barry N
BN
Madiraju
Murty V V S
MV
D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002876:Chromosomes, Bacterial; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D010957:Plasmids; D018741:Replication Origin
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria