Accueil du site > Animations Scientifiques > Séminaires 2011 > Maïté Coppey — Evidence of spatio-temporal fluctuations of supranucleosomal state regulating accessibility of bromodomain to acetylated H4 in living cells by high-resolution FLIM
Maïté Coppey — Evidence of spatio-temporal fluctuations of supranucleosomal state regulating accessibility of bromodomain to acetylated H4 in living cells by high-resolution FLIM
Speaker :
Maïté Coppey, Institut Jacques Monod, Paris
When :
Wednesday 26 January at 11am
Where :
C023 (RDC LR6 côté Centre Blaise Pascal)
Title :
Evidence of spatio-temporal fluctuations of supranucleosomal state regulating accessibility of bromodomain to acetylated H4 in living cells by high-resolution FLIM
Abstract :
We unveiled spatio-temporal fluctuations of the fluorescence lifetime of EGFP-histone H4 in living cells (HEK 293) by using fast time-lapse FLIM measurement and two-photon excitation. We showed that these fluctuations are likely due to the variations of the microenvironment of the EGFP-H4 incorporated in chromatin and thus reflect the variations of a supra-nucleosomal state of chromatin domains of about 0.6 micron of diameter. Interestingly, the interaction between the double bromodomain of TAFII250 and the acetylated histone H4 exhibit similar spatio-temporal fluctuations. Furthermore, no interactions can be detected when chromatin is shifted to a “close” supra-nucleosomal state characterized by short fluorescence lifetime of EGFP-H4, after ATP depletion. A detailed pixel by pixel analysis over 100 time-lapse FLIM images revealed the existence of a correlation between the temporal mean value and the amplitude of the fluctuations of fluorescence lifetime of EGFP-H4. Spatial mapping of this correlation unveiled a more dynamical chromatin at the nucleus periphery. We propose that these fluctuations of supra-nucleosomal state would modulate the accessibility of protein factors to nucleosomes and thus likely correspond to a switch between “open” and “close” states of chromatin domain.
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