The Interactome Model of RNA Transcription and Spliceosome. A. The protein factory model of RNA Polymerase II and spliceosome. B. The T7 polymerase model without interacting with spliceosome. C. to E. Simulations of the in vitro RNA splicing assay. Black squares: measured premRNA; Solid lines: simulated pre-mRNA curves; Black triangles: measured mature mRNA; Dotted lines: simulated mRNA curves. Black bars: standard deviations of data. The interactome of Pol II and spliceosome (NEs) increases the affinity of NEs to the pre-mRNA (smaller Km) as demonstrated by perturbing Km (NEs to pre-mRNA). The value is 50 nM in C and 1 nM in D while Km (RNase to pre-mRNA) is 50 nM in both cases. D. The pre-mRNA protected by PolII interactome is in steady state to maintain mature mRNA production. E. The viral T7 polymerase simulation. Mature mRNA is rapid degraded without protection. Km (NEs to pre-mRNA) = Km (RNase to pre-mRNA) = 50 nM.