title: Dynamics of the p53-Mdm2 feedback loop in individual cells.
abstract: The tumor suppressor p53, one of the most intensely investigated proteins, is usually studied by experiments that are averaged over cell populations, potentially masking the dynamic behavior in individual cells. We present a system for following, in individual living cells, the dynamics of p53 and its negative regulator Mdm2 (refs. 1,4-7): this system uses functional p53-CFP and Mdm2-YFP fusion proteins and time-lapse fluorescence microscopy. We found that p53 was expressed in a series of discrete pulses after DNA damage. Genetically identical cells had different numbers of pulses: zero, one, two or more. The mean height and duration of each pulse were fixed and did not depend on the amount of DNA damage. The mean number of pulses, however, increased with DNA damage. This approach can be used to study other signaling systems and suggests that the p53-Mdm2 feedback loop generates a 'digital' clock that releases well-timed quanta of p53 until damage is repaired or the cell dies.
authors.affiliation: Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Galit
authors.initials: G
authors.lastname: Lahav
authors.forename: Nitzan
authors.initials: N
authors.lastname: Rosenfeld
authors.forename: Alex
authors.initials: A
authors.lastname: Sigal
authors.forename: Naama
authors.initials: N
authors.lastname: Geva-Zatorsky
authors.forename: Arnold J
authors.initials: AJ
authors.lastname: Levine
authors.forename: Michael B
authors.initials: MB
authors.lastname: Elowitz
authors.forename: Uri
authors.initials: U
authors.lastname: Alon
mesh_terms: D004307:Dose-Response Relationship, Radiation; D025461:Feedback, Physiological / Q000502:physiology* / Q000528:radiation effects; D005260:Female; D005720:Gamma Rays; D006801:Humans; D015151:Immunoblotting; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000378:metabolism* / Q000528:radiation effects; D051736:Proto-Oncogene Proteins c-mdm2; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2