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Proc Natl Acad Sci U S A. 2013 Jul 30;110(31):12619-24. doi: 10.1073/pnas.1308270110. Epub 2013 Jul 15.

Structure and function of CarD, an essential mycobacterial transcription factor.

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Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065, USA.


CarD, an essential transcription regulator in Mycobacterium tuberculosis, directly interacts with the RNA polymerase (RNAP). We used a combination of in vivo and in vitro approaches to establish that CarD is a global regulator that stimulates the formation of RNAP-holoenzyme open promoter (RPo) complexes. We determined the X-ray crystal structure of Thermus thermophilus CarD, allowing us to generate a structural model of the CarD/RPo complex. On the basis of our structural and functional analyses, we propose that CarD functions by forming protein/protein and protein/DNA interactions that bridge the RNAP to the promoter DNA. CarD appears poised to interact with a DNA structure uniquely presented by the RPo: the splayed minor groove at the double-stranded/single-stranded DNA junction at the upstream edge of the transcription bubble. Thus, CarD uses an unusual mechanism for regulating transcription, sensing the DNA conformation where transcription bubble formation initiates.


initiation; mycobacteria; ribosomal RNA (rRNA); transcription activator

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