Association with coregulators is the major determinant governing peroxisome proliferator-activated receptor mobility in living cells.
The nucleus is an extremely dynamic compartment, and protein mobility represents a key factor in transcriptional regulation. We showed in a previous study that the diffusion of peroxisome proliferator-activated receptors (PPARs), a family of nuclear receptors regulating major cellular and metabolic functions, is modulated by ligand binding. In this study, we combine fluorescence correlation spectroscopy, dual color fluorescence cross-correlation microscopy, and fluorescence resonance energy transfer to dissect the molecular mechanisms controlling PPAR mobility and transcriptional activity in living cells. First, we bring new evidence that in vivo a high percentage of PPARs and retinoid X receptors is associated even in the absence of ligand. Second, we demonstrate that coregulator recruitment (and not DNA binding) plays a crucial role in receptor mobility, suggesting that transcriptional complexes are formed prior to promoter binding. In addition, association with coactivators in the absence of a ligand in living cells, both through the N-terminal AB domain and the AF-2 function of the ligand binding domain, provides a molecular basis to explain PPAR constitutive activity.
Tudor
Cicerone
C
Laboratory of Biomolecular Dynamics, Katholieke Universiteit, Leuven B-3001, Belgium.
Feige
Jérôme N
JN
Center for Integrative Genomics, National Research Center "Frontiers in Genetics," University of Lausanne, Lausanne CH-1015, Switzerland, and.
Pingali
Harikishore
H
Zydus Research Centre, Ahmedabad 382210, India.
Lohray
Vidya Bhushan
VB
Zydus Research Centre, Ahmedabad 382210, India.
Wahli
Walter
W
Center for Integrative Genomics, National Research Center "Frontiers in Genetics," University of Lausanne, Lausanne CH-1015, Switzerland, and.
Desvergne
Béatrice
B
Center for Integrative Genomics, National Research Center "Frontiers in Genetics," University of Lausanne, Lausanne CH-1015, Switzerland, and.
Engelborghs
Yves
Y
Laboratory of Biomolecular Dynamics, Katholieke Universiteit, Leuven B-3001, Belgium. Electronic address: yves.engelborghs@fys.kuleuven.be.
Gelman
Laurent
L
Center for Integrative Genomics, National Research Center "Frontiers in Genetics," University of Lausanne, Lausanne CH-1015, Switzerland, and. Electronic address: laurent.gelman@fmi.ch.
D000818:Animals; D031541:Fluorescence Resonance Energy Transfer; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D009687:Nuclear Proteins / Q000378:metabolism; D047492:Peroxisome Proliferator-Activated Receptors / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D047488:Retinoid X Receptors / Q000378:metabolism*
D008024:Ligands; D009687:Nuclear Proteins; D047492:Peroxisome Proliferator-Activated Receptors; D047488:Retinoid X Receptors