Fig. 4: U1-C promotes and stabilizes the binding of a -1A RNA to U1 snRNP.

A Dose response curves of 9bp-1A RNA binding to U1 snRNP vs. U1-C concentration. The red line and shading indicate the fit and 95% CI to the fitted equation to estimate an EC₅₀ value (1.3 ± 0.20 nM). B Cumulative probability distribution of unbound dwell times at 1 nM 9bp-1A RNA across U1-C concentrations (0 nM, N = 3106; 0.1 nM, N = 2920; 1 nM, N = 5543; 10 nM, N = 3169; 100 nM, N = 5154). C Unbound time constants (\({\tau }_{U}\)) determined from MLE of a monoexponential distribution for unbound dwell times overlaid with a fit to the fitted equation (EC₅₀ = 1.8 ± 0.5 nM). Plotted \({\tau }_{U}\) values (circles) are shown as mean ± SEM and are computed across all single molecules for each U1-C concentration (0 nM, N = 2381; 0.1 nM, N = 2247; 1 nM, N = 4764; 10 nM, N = 3105; 100 nM, N = 5216). The fitted equation is shown as the fit (solid line) and 95% confidence interval of the fit (shaded region). D Cumulative probability distribution of bound dwell times at 1 nM 9bp-1A RNA across U1-C concentrations (0 nM, N = 2381; 0.1 nM, N = 2247; 1 nM, N = 4764; 10 nM, N = 3105; 100 nM, N = 5216). E Cumulative probability distribution of bound dwell times at 1 nM 9bp-1A RNA and 100 nM U1-C (grey circles overlaid with MLE of mono (blue dashed) and biexponential distributions (solid red). F MLE of bound time constants (\({\tau }_{B}^{1}\) and \({\tau }_{B}^{2}\), left) and amplitude of \({\tau }_{B}^{2}\) (right) of a biexponential distribution for bound dwell times at 1 nM 9bp-1A RNA across U1-C concentrations (mean ± SEM). The amplitudes of \({\tau }_{B}^{2}\) are overlaid with the with a fit to the fitted equation (EC₅₀ = 1.0 ± 0.2 nM). The fitted equation is shown as the fit (solid line) and 95% confidence interval of the fit (shaded region). Plotted parameters and errors are computed across all single molecules for each U1-C concentration (0 nM, N = 2381; 0.1 nM, N = 2247; 1 nM, N = 4764; 10 nM, N = 3105; 100 nM, N = 5216). G Contour plots showing the correlation between successive bound event durations (\(i\) and \(i+1\)) within individual molecules. Dashed line is the identity line. Source data are provided as Source data file.