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EMBO J. 2017 Sep 15;36(18):2710-2725. doi: 10.15252/embj.201696035. Epub 2017 Jul 19.

Coactivators and general transcription factors have two distinct dynamic populations dependent on transcription.

Vosnakis N1,2,3,4, Koch M1,2,3,4, Scheer E1,2,3,4, Kessler P1,2,3,4, Mély Y4,5, Didier P4,5, Tora L6,2,3,4.

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Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.
Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.
Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.
Université de Strasbourg, Illkirch, France.
Laboratoire de Biophotonique et Pharmacologie, Illkirch, France.
Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France


SAGA and ATAC are two distinct chromatin modifying co-activator complexes with distinct enzymatic activities involved in RNA polymerase II (Pol II) transcription regulation. To investigate the mobility of co-activator complexes and general transcription factors in live-cell nuclei, we performed imaging experiments based on photobleaching. SAGA and ATAC, but also two general transcription factors (TFIID and TFIIB), were highly dynamic, exhibiting mainly transient associations with chromatin, contrary to Pol II, which formed more stable chromatin interactions. Fluorescence correlation spectroscopy analyses revealed that the mobile pool of the two co-activators, as well as that of TFIID and TFIIB, can be subdivided into "fast" (free) and "slow" (chromatin-interacting) populations. Inhibiting transcription elongation decreased H3K4 trimethylation and reduced the "slow" population of SAGA, ATAC, TFIIB and TFIID In addition, inhibiting histone H3K4 trimethylation also reduced the "slow" populations of SAGA and ATAC Thus, our results demonstrate that in the nuclei of live cells the equilibrium between fast and slow population of SAGA or ATAC complexes is regulated by active transcription via changes in the abundance of H3K4me3 on chromatin.


FCS ; FLIP ; FRAP ; diffusion constant; tudor domain

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