The transcriptional co-activator LEDGF/p75 displays a dynamic scan-and-lock mechanism for chromatin tethering.
Nearly all cellular and disease related functions of the transcriptional co-activator lens epithelium-derived growth factor (LEDGF/p75) involve tethering of interaction partners to chromatin via its conserved integrase binding domain (IBD), but little is known about the mechanism of in vivo chromatin binding and tethering. In this work we studied LEDGF/p75 in real-time in living HeLa cells combining different quantitative fluorescence techniques: spot fluorescence recovery after photobleaching (sFRAP) and half-nucleus fluorescence recovery after photobleaching (hnFRAP), continuous photobleaching, fluorescence correlation spectroscopy (FCS) and an improved FCS method to study diffusion dependence of chromatin binding, tunable focus FCS. LEDGF/p75 moves about in nuclei of living cells in a chromatin hopping/scanning mode typical for transcription factors. The PWWP domain of LEDGF/p75 is necessary, but not sufficient for in vivo chromatin binding. After interaction with HIV-1 integrase via its IBD, a general protein-protein interaction motif, kinetics of LEDGF/p75 shift to 75-fold larger affinity for chromatin. The PWWP is crucial for locking the complex on chromatin. We propose a scan-and-lock model for LEDGF/p75, unifying paradoxical notions of transcriptional co-activation and lentiviral integration targeting.
Hendrix
Jelle
J
Laboratory for Biomolecular Dynamics, University of Leuven, Leuven, Flanders, B-3000, Belgium.
Gijsbers
Rik
R
De Rijck
Jan
J
Voet
Arnout
A
Hotta
Jun-ichi
J
McNeely
Melissa
M
Hofkens
Johan
J
Debyser
Zeger
Z
Engelborghs
Yves
Y
D002843:Chromatin / Q000378:metabolism*; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000032:analysis
D002843:Chromatin; D005456:Fluorescent Dyes; D036341:Intercellular Signaling Peptides and Proteins; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; C119380:lens epithelium-derived growth factor; D049452:Green Fluorescent Proteins