| Regulation of the M. tuberculosis
hypoxic response gene encoding alpha-crystallin
David R. Sherman,1 Martin Voskuil2, Dirk Schnappinger2, Reiling Liao,1 Maria I. Harrell,1 and Gary K. Schoolnik2* 1Department of Pathobiology, University of Washington, Seattle, WA 98195, USA. and 2 Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA.
Abstract: Unlike many pathogens that are overtly toxic to their hosts, the primary virulence determinant of Mycobacterium tuberculosis appears to be its ability to persist for years or decades within humans in a clinically latent state. Since early in the 20th century latency has been linked to hypoxic conditions within the host, but the response of M. tuberculosis to a hypoxic signal remains poorly characterized. The M. tuberculosis alpha-crystallin (acr) gene is powerfully and rapidly induced at reduced oxygen tensions, providing us a means to identify regulators of the hypoxic response. Using a whole genome microarray, we identified >100 genes whose expression is rapidly altered by defined hypoxic conditions. Numerous genes involved in biosynthesis and aerobic metabolism are repressed, while a high proportion of the induced genes have no known function. Among the induced genes is an apparent operon including the putative two-component response regulator pair Rv3133c/Rv3132c. When we interrupted expression of this operon by targeted disruption of the upstream gene Rv3134c, the hypoxic regulation of acr was eliminated. These results suggest a possible role for Rv3132c/3133c/3134c in mycobacterial latency |