The −35 and −10 boxes are underlined, and the ATG start codon of secG is indicated by a box. Figure 4 Primer extension

TPX-0005 solubility dmso and 5’ RACE analysis of the rnr genomic region. (a) Primer extension was carried out with 5 μg of total RNA extracted from the RNase R- strain at 15°C, using a 5’-end-labeled primer specific for the 5’Selleck Tideglusib region of smpB (rnm002). The arrows indicate the fragments (a – 188bp, b – 182bp) extended from this primer. The comparison of the fragments sizes with the reading of a generated M13 sequencing reaction provided the determination of the 5’-end of the obtained mRNAs. (b) 5’ RACE mapping of the smpB transcript. Reverse transcription was carried out on 6 μg of total RNA extracted from wild type and mutant derivatives as indicated on top, using an smpB specific primer (rnm011). PCR signals upon treatment with TAP (lane T+) or without treatment (lane T-) were separated in a 3 % agarose gel. As a negative control, the same experiments were

performed in the SmpB- strain. The arrows indicate the specific 5’ RACE products (1, 2). Molecular weight marker (Hyperladder – Bioline) is shown on the left. (c) Sequence of the region that comprises the 3’end of rnr and the 5’end of Oligomycin A order smpB. The nucleotides corresponding to the 5’-end of the extended fragments or to the 5’ RACE products are highlighted in bold. Letters (a, b) or numbers (1, 2) denote primer extension or 5’ RACE results, respectively. The ATG of smpB and the stop codon of rnr (TAA) are delimited by a dashed box and the putative RBS is indicated. The fact that the same pattern was obtained from wild type of and

RNase R- samples (Figure 4b) further confirms that the processing of the rnr/smpB transcript is not affected in the RNase R- strain. Taken together these results indicate that the pneumococcal rnr transcript is expressed as part of an extensive operon. This large transcript is most probably subject to a complex regulation with several promoters and multiple processing events leading to smaller transcripts. Indeed, a promoter identified upstream secG may be responsible for the independent regulation of the downstream genes, secG, rnr and smpB. Processing of the operon to yield mature gene products is likely to occur. Since we could not identify other active promoters upstream rnr or smpB, we believe that transcription of rnr and smpB does not occur independently and is most probably driven by the promoter identified upstream of secG. SmpB mRNA and protein levels are modulated by RNase R We have just seen that in S. pneumoniae rnr is co-transcribed with smpB. On the other hand, in E. coli SmpB was shown to modulate the stability of RNase R [28]. In E. coli processing of tmRNA under cold-shock is dependent on RNase R [12], and this enzyme has also been involved in tmRNA degradation in C. crescentus and P. syringae[23, 24]. Thus, we were interested in clarifying which could be the involvement of RNase R with the main components of the trans-translation system in S. pneumoniae.