title: The DNA binding activity of p53 displays reaction-diffusion kinetics.
abstract: The tumor suppressor protein p53 plays a key role in maintaining the genomic stability of mammalian cells and preventing malignant transformation. In this study, we investigated the intracellular diffusion of a p53-GFP fusion protein using confocal fluorescence recovery after photobleaching. We show that the diffusion of p53-GFP within the nucleus is well described by a mathematical model for diffusion of particles that bind temporarily to a spatially homogeneous immobile structure with binding and release rates k1 and k2, respectively. The diffusion constant of p53-GFP was estimated to be Dp53-GFP=15.4 microm2 s-1, significantly slower than that of GFP alone, DGFP=41.6 microm2 s-1. The reaction rates of the binding and unbinding of p53-GFP were estimated as k1=0.3 s-1 and k2=0.4 s-1, respectively, values suggestive of nonspecific binding. Consistent with this finding, the diffusional mobilities of tumor-derived sequence-specific DNA binding mutants of p53 were indistinguishable from that of the wild-type protein. These data are consistent with a model in which, under steady-state conditions, p53 is latent and continuously scans DNA, requiring activation for sequence-specific DNA binding.
authors.affiliation: Department of Mathematics, Vanderbilt University, and Department of Biochemistry, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Nashville, Tennessee, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Hinow
authors.forename: Carl E
authors.initials: CE
authors.lastname: Rogers
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Barbieri
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Pietenpol
authors.forename: Anne K
authors.initials: AK
authors.lastname: Kenworthy
authors.forename: Emmanuele
authors.initials: E
authors.lastname: DiBenedetto
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D001665:Binding Sites; D002467:Cell Nucleus / Q000737:chemistry* / Q000378:metabolism*; D003198:Computer Simulation; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D004058:Diffusion; D007700:Kinetics; D008954:Models, Biological; D008956:Models, Chemical; D011485:Protein Binding; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D016159:Tumor Suppressor Protein p53; D004247:DNA