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Biochem Soc Trans. 2009 February ; 37(Pt 1): 123–126.


Copyright 2009 by the Authors. Journal compilation (c) 2009 Biochemical Society.


TA (toxin–antitoxin) loci are ubiquitous in prokaryotic microorganisms, including archaea, yet

their physiological function is largely unknown. For example, preliminary reports have suggested

that TA loci are microbial stress-response elements, although it was recently shown that knocking

out all known chromosomally located TA loci in Escherichia coli did not have an impact on

survival under certain types of stress. The hyperthermophilic crenarchaeon Sulfolobus solfataricus

encodes at least 26 vapBC (where vap is virulence-associated protein) family TA loci in its

genome. VapCs are PIN (PilT N-terminus) domain proteins with putative ribonuclease activity,

while VapBs are proteolytically labile proteins, which purportedly function to silence VapCs when

associated as a cognate pair. Global transcriptional analysis of S. solfataricus heat-shock-response

dynamics (temperature shift from 80 to 90°C) revealed that several vapBC genes were triggered

by the thermal shift, suggesting a role in heat-shock-response. Indeed, knocking out a specific

vapBC locus in S. solfataricus substantially changed the transcriptome and, in one case, rendered

the crenarchaeon heat-shock-labile. These findings indicate that more work needs to be done to

determine the role of VapBCs in S. solfataricus and other thermophilic archaea, especially with

respect to post-transcriptional regulation.

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