Candidate motifs identified upstream of the ribosomal protein genes, upstream location, site-directed mutagenesis and results of reporter assays. Motif RPA (TRP-1) does not influence reporter activity, and motif RPB (TRP-2) acts as an enhancer of gene-expression from the RPL9 promoter. (a) Sequence logos represent the consensus sequence for each candidate motif. The y-axis represents information content at each position. (b) Occurrences and positions of the motifs in the promoter region relative to the translational start site of each gene. The gene names are abbreviated as shown in Table 1. The underlined gene name indicates the representative promoter used in the reporter assays. (c) The WT motifs and their mutagenized (MUT) versions in the representative promoter are represented. (d) The graphs depict luciferase activity as ratios of firefly:renilla activity in relative luciferase units (RLU) from the different constructs containing either WT or mutagenized versions of RPA, RPB, both motifs or both copies of motif RPB. All luciferase readings are relative to an internal control (α-tubulin-renilla). Error bars represent standard error calculated across the means of three independent electroporations. p-values describe the probability that the difference in expression between the WT and mutagenized promoters may be due to chance.
Mullapudi et al. Genome Biology 2009 10:R34 doi:10.1186/gb-2009-10-4-r34