Mycobacterium tuberculosis WhiB3 interacts with RpoV to affect host survival but is dispensable for in vivo growth.
Previous work established that the principal sigma factor (RpoV) of virulent Mycobacterium bovis, a member of the Mycobacterium tuberculosis complex, restores virulence to an attenuated strain containing a point mutation (Arg-515-->His) in the 4.2 domain of RpoV. We used the 4.2 domain of RpoV as bait in a yeast two-hybrid screen of an M. tuberculosis H37Rv library and identified a putative transcription factor, WhiB3, which selectively interacts with the 4.2 domain of RpoV in virulent strains but not with the mutated (Arg-515-->His) allele. Infection of mice and guinea pigs with a M. tuberculosis H37Rv whiB3 deletion mutant strain showed that whiB3 is not necessary for in vivo bacterial replication in either animal model. In contrast, an M. bovis whiB3 deletion mutant was completely attenuated for growth in guinea pigs. However, we found that immunocompetent mice infected with the M. tuberculosis H37Rv whiB3 mutant strain had significantly longer mean survival times as compared with mice challenged with wild-type M. tuberculosis. Remarkably, the bacterial organ burdens of both mutant and wild-type infected mice were identical during the acute and persistent phases of infection. Our results imply that M. tuberculosis replication per se is not a sufficient condition for virulence in vivo. They also indicate a different role for M. bovis and M. tuberculosis whiB3 genes in pathogenesis generated in different animal models. We propose that M. tuberculosis WhiB3 functions as a transcription factor regulating genes that influence the immune response of the host.
Steyn
Adrie J C
AJ
Harvard School of Public Health, Department of Immunology and Infectious Disease, Boston, MA 02115, USA.
Collins
Desmond M
DM
Hondalus
Mary K
MK
Jacobs
William R
WR
Kawakami
R Pamela
RP
Bloom
Barry R
BR
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D006168:Guinea Pigs; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009163:Mycobacterium bovis / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013154:Spleen / Q000473:pathology; D014157:Transcription Factors; D014397:Tuberculosis, Pulmonary / Q000382:microbiology / Q000401:mortality / Q000473:pathology; D020798:Two-Hybrid System Techniques
D001426:Bacterial Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C121354:WhiB3 protein, Mycobacterium smegmatis; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases