Level fluctuations induced by transcriptional noise in a system with N = 2 ceRNA species and M = 1 miRNA species. We took Gaussian distributions for the transcription rates β, b1, and b2, keeping the ratio between the average and the width fixed in each case. All parameters and distributions of rates are also kept fixed, except for the miRNA transcription rate distribution P(β), which is parameterized by its average value . In this case: , , , , σ1 = σ2 = 10, and κ1 = κ2 = 1. (Top) Normalized fluctuations (ratio between the width of the fluctuations in the interacting and the noninteracting system, the latter corresponding to ) for uncorrelated distributions of transcription rates. (Center) Ratio between the normalized fluctuations of the level of ceRNA 1 obtained in the presence of correlations and in the uncorrelated case. (Yellow line) Maximal anti-correlation between b1 and b2 (Σ12 = −1); (purple line) maximal correlation between b1 and β (Σ13 = 1); and (blue line) maximal correlation between b2 and β (Σ23 = 1). (Bottom) Average molecular levels.