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Transcription factors modulate c-Fos transcriptional bursts
by Adrien Senecal (IBENS, Paris)
In most cells, transcription has been shown to occur in episodic bursts. The molecular mechanisms underlying these bursts are not yet fully understood. A major role has been attributed to the local chromatin environment, but the impact of transcription factors (TF) remains largely unknown. As a model, we investigated the c-Fos proto-oncogene response to MAPK stimuli and synthetic TF based on Transcription activator-like effectors (TALE). Using single molecule FISH, we observed uncorrelated bursts of transcription on individual alleles. The average number of nascent mRNA per active transcription site was a characteristic of the stimulation. The amplitude of the bursts is not a predefined property of the promoter but can be adjusted depending on the TF. Moreover, the frequency of the bursts is regulated by the nuclear concentration of the TF. Transcription is thus regulated both at the level of burst amplitude and frequency by TF.