page_title: Αr14 RNA
section_title: Promoter Analysis
hierarchical_section_title: Αr14 RNA / Promoter Analysis
context_page_description: αr14 is a family of bacterial small non-coding RNAs with representatives in a broad group of α-proteobacteria. The first member of this family was found in a Sinorhizobium meliloti 1021 locus located in the chromosome. It was later renamed NfeR1 and shown to be highly expressed in salt stress and during the symbiotic interaction on legume roots. Further homology and structure conservation analysis identified 2 other chromosomal copies and 3 plasmidic ones. Moreover, full-length Smr14C homologs have been identified in several nitrogen-fixing symbiotic rhizobia, in the plant pathogens belonging to Agrobacterium species as well as in a broad spectrum of Brucella species. αr14C RNA species are 115-125 nt long and share a well defined common secondary structure. Most of the αr14 transcripts can be catalogued as trans-acting sRNAs expressed from well-defined promoter regions of independent transcription units within intergenic regions of the α-proteobacterial genomes.
context_section_description: All the promoter regions of the αr14 family members examined so far are very conserved in a sequence stretch extending up to 120 bp upstream of the transcription start site of the sRNA. All closest homolog loci have recognizable σ70-dependent promoters showing a -35/-10 consensus motif CTTAGAC-n17-CTATAT, which has been previously shown to be widely conserved among several other genera in the α-subgroup of proteobacteria. To identify binding sites for other known transcription factors we used the fasta sequences provided by RegPredict(http://regpredict.lbl.gov/regpredict/help.html), and used those position weight matrices (PSWM) provided by RegulonDB  (http://regulondb.ccg.unam.mx). We built PSWM for each transcription factor from the RegPredict sequences using the Consensus/Patser program, choosing the best final matrix for motif lengths between 14–30 bps a threshold average E-value < 10E-10 for each matrix was established, (see "Thresholded consensus" in http://gps-tools2.its.yale.edu). Moreover, we searched for conserved unknown motifs using MEME (http://meme.sdsc.edu/meme4_6_1/intro.html) and used relaxed regular expressions (i.e. pattern matching) over all Smr14C2 homologs promoters. 
  This studies revealed two well defined groups of loci, the first one represented by the closest homologs (Figure 5) that presented a 26 bp long region very conserved between positions -40 and -75, marked as conserved MEME motif in (Figure 5), but no significant similarity to known transcription factor binding sites matrices could be established. A group of not so closely related members of the αr14 family constituted the second group of conserved promoters (Figure6). They presented a different promoter region, very well conserved across all members and an additional unknown 20 bp motif.
caption: Figure 5: Graphic representation of the αr14 seed members' promoter region. All members presented putative σ70 promoters with -30 and -10 boxes marked in green and red respectively.
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