Variations in the multiple tbp genes in different Halobacterium salinarum strains and their expression during growth
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ORIGINAL PAPER
Variations in the multiple tbp genes in diVerent Halobacterium salinarum strains and their expression during growth Katharina Teufel · Anne Bleiholder · Tim Griesbach · Felicitas Pfeifer
Received: 4 January 2008 / Revised: 23 April 2008 / Accepted: 29 April 2008 / Published online: 28 May 2008 © Springer-Verlag 2008
Abstract The presence and expression of the multiple tbp genes encoding TATA-box binding proteins (TBPs) was investigated in various strains and mutants of the archaeon Halobacterium salinarum. Six genes, tbpA through tbpF, are present in the genome of Hbt. salinarum NRC-1 and also in the gas vesicle negative mutant strain R1. The only tbp gene located in the chromosome is tbpE, whereas all others are found in the plasmid DNA. Due to the dynamic nature of the plasmids in the Halobacterium strains, the copy numbers of the alternative tbp genes vary signiWcantly. Five tbp genes (tbpA through tbpE) were present in the wild-type strain Hbt. salinarum PHH1. The tbpC gene of Hbt. salinarum PHH1 carried an ISH27-2 insertion element at the start of the reading frame that prevented the expression. All other tbp genes of PHH1 were expressed under aerobic and anaerobic growth conditions and quantitative RT-PCR yielded tbpE as dominant tbp transcript during the exponential growth phase. The plasmid deletion variant Hbt. salinarum PHH4 lacked all of the tbp genes except for tbpE and showed an altered growth behaviour compared to PHH1 wild-type in the stationary growth phase under anaerobic growth conditions. Keywords TBP proteins · Plasmid variation · ISH elements · Alternative tbp genes
Communicated by Jan RoeloV van der Meer. K. Teufel · A. Bleiholder · T. Griesbach · F. Pfeifer (&) Institute for Microbiology and Genetics, Technische Universität Darmstadt, Schnittspahnstr. 10, 64287 Darmstadt, Germany e-mail: [email protected]
Abbreviations TBP TATA-box binding protein RNAP RNA polymerase TFB Transcription factor B qRT-PCR Quantitative reverse transcriptase polymerase chain reaction
Introduction The basal transcription apparatus of Archaea comprises a single, multi-subunit RNA polymerase (RNAP) related to the eukaryal RNAP II that is recruited to the archaeal promoter with the help of two proteins, the TATA-box binding protein TBP and TFB, a homolog of the eukaryal transcription factor TFIIB (Thomm 1996; Bell et al. 1999). Hyperthermophilic and methanogenic Archaea usually contain single tbp and single or few tfb genes, but multiple and divergent genes encoding TBP and TFB proteins are present in the sequenced genomes of Halobacterium salinarum strains NRC-1 and the gas vesicle-negative mutant strain R1 (Ng et al. 2000; Halolex database, http://www.halolex.mpg.de; PfeiVer et al. 2008b). It has been suggested that the multiple Halobacterium TFB and TBP proteins initiate transcription at diVerent promoters (or under diVerent growth conditions) and inXuence the gene regulation, similar to the multiple sigma factors involved in the gene regulation of bacteria (Baliga et al. 2000). With res
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