Global Transcriptional and Proteomic Analysis of the Sig1 Heat Shock Regulon ofDeinococcus radiodurans

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Abstract
Thesig1gene, predicted to encode an extracytoplasmic function-type heat shock sigma factor ofDeinococcus radiodurans, has been shown to play a central role in the positive regulation of the heat shock operonsgroESLanddnaKJ.To determine if Sig1 is required for the regulation of additional heat shock genes, we monitored the global transcriptional and proteomic profiles of aD. radioduransR1sig1mutant and wild-type cells in response to elevated temperature stress. Thirty-one gene products were identified that showed heat shock induction in the wild type but not in thesig1mutant. Quantitative real-time PCR experiments verified the transcriptional requirement of Sig1 for the heat shock induction of the mRNA of five of these genes—dnaK,groES, DR1314,pspA, andhsp20. hsp20appears to encode a new member of the small heat shock protein superfamily, DR1314 is predicted to encode a hypothetical protein with no recognizable orthologs, andpspAis predicted to encode a protein involved in maintenance of membrane integrity. Deletion mutation analysis demonstrated the importance in heat shock protection ofhsp20and DR1314. The promoters ofdnaKJE,groESL, DR1314,pspA, andhsp20were mapped and, combined with computer-based pattern searches of the upstream regions of the 26 other Sig1 regulon members, these results suggested that Sig1 might recognize both σ70-type and σW-type promoter consensus sequences. These results expand theD. radioduransSig1 heat shock regulon to include 31 potential new members, including not only factors with cytoplasmic functions, such asgroESanddnaK, but also those with extracytoplasmic functions, likepspA.