Figure 2

Dynamic partitioning of TFIIH in the nucleoplasm. Quantitative visualization and analysis of the fluorescently-tagged transcription factor IIH (TFIIH) molecules in living cells [69] suggest that TFIIH partitions dynamically among at least four distinct molecular pools in the nucleoplasm: a freely diffusing "unemployed" pool, RNA polymerase I and II transcription sites, and DNA repair sites. A) In the absence of DNA damage (UV^-), the average residence times of TFIIH employed in transcription are approximately 25 and 5 seconds for the sites of RNA pol I and II, correspondingly. B) Upon DNA damage (UV⁺), TFIIH reversibly repartitions into DNA repair sites, where its average residence time is significantly longer, 240 seconds, while transcription ceases in the meantime. As the steady-state level of TFIIH in the cell is tightly controlled, the competitive partitioning of TFIIH between different functional pools may potentially couple and coordinate such cellular functions as transcription and DNA repair, both locally and globally. The dynamic partitioning of TFIIH is one of the concrete examples of how the fluxes of moonlighting activities, driven by essentially economic supply-and-demand-type relationships, can lead to a seamless and "design-free" integration of diverse cellular functions into one dynamic and adaptive functional whole that performs and evolves as a self-organizing molecular-scale economy.