Rapid switching of TFIIH between RNA polymerase I and II transcription and DNA repair in vivo

The transcription/repair factor TFIIH operates as a DNA helix opener in RNA polymerase II (RNAP2) transcription and nucleotide excision repair. To study TFIIH in vivo, we generated cell lines expressing functional GFP-tagged TFIIH. TFIIH was homogeneously distributed throughout the nucleus with nucleolar accumulations. We provide in vivo evidence for involvement of TFIIH in RNA polymerase I (RNAP1) transcription. Photobleaching revealed that TFIIH moves freely and gets engaged in RNAP1 and RNAP2 transcription for similar to25 and similar to6 s, respectively. TFIIH readily switches between transcription and repair sites (where it is immobilized for similar to4 min) without large-scale alterations in composition. Our findings support a model of diffusion and random collision of individual components that permits a quick and versatile response to changing conditions.