Thermophiles transcription

Analysis of the sequences located upstream of archaeal rRNA genes has shown that archaeal rRNA promoters consist of the sequence TTTA(A/T)A located 20-30 nucleotides upstream of the transcription initiation site and a weakly conserved sequence, (A/T)TG(A/C) around the transcription initiation site [40]. Transcription of the rRNA genes terminates within pyrimidine-rich regions in the extreme thermophiles [30,41], in pyrimidine-rich regions followed by a short hairpin loop in the methanogens [27,34] and in AT-rich regions preceded by a GC-rich region in the extreme... 

Archaeal promoters resemble the RNAIl promoters of the eucarya [40,161] and are different from those in the bacteria [162]. Analysis of the promoters of archaeal r-protein genes shows the presence of two conserved regions a hexanucleotide sequence (TTTAAA/T) located 20-30 nucleotides upstream of the transcription initiation site and two conserved nucleotides around the transcription initiation site (shown in lower case (Ta/gT/G)) [9,114,120,141,144,145,148,150]. Transcription in the archaea usually starts at a purine residue as is the case in the other two domains [161,162]. The presence of several initiation sites is common among the extreme thermophiles [120,141,148], a situation similar to that found for yeast r-proteins genes [156]. 

The sequences immediately upstream from the open reading frames of both the sulfo-thermophiles and the thermophilic methanogens are presented in Table 7. Stretches of purines located 3-9 nucleotides upstream from the start codon which could interact with the polypyrimidine sequence present at the 3 terminus of each archaeal 16S rRNA (Shine Dalgamo interaction) are underlined. For the thermophilic methanogen transcripts, as for those of the methanogen and extreme halophiles [1], a purine-rich sequence, of varying length, is present at the appropriate position. However, for the sulfothermophiles... 

Transcripts of 5S rRNAs and tRNAs generally start just before and terminate immediately after single genes amongst sulfothermophiles, while these stable RNA genes are often clustered in transcriptional units in the thermophilic methanogens and other archaea. 

Falentin, H., Henaff, N., Le Bivic, P, et al. (2012) Reverse transcription quantitative PCR revealed persistency of thermophilic lactic acid bacteria metabolic activity until the end of the ripening of Emmental cheese. Food Microbiol... 

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