Phosphorylation of serines 15 and 37 is necessary for efficient accumulation of p53 following irradiation with UV.
Changes in the phosphorylation state of p53 are important in increasing its half-life and potency as a transcription factor. To investigate their roles, serine residues 15 and 37 were mutated to alanines and the mutated proteins were expressed stably at low basal levels in Li-Fraumeni-derived p53-null human fibroblasts. The accumulation of p53 after DNA damage was analysed quantitatively in multiple clones. Mutation of serine 15, serine 37 or both impaired the accumulation of the protein after exposing the cells to ultraviolet radiation (50-100% increase for the mutant proteins, 500% increase for wild-type p53) but not after treatment with adriamycin. The diminished accumulation of mutant p53 protein is due to a reduction of basal HDM association. Analysis of p53-dependent transcription revealed that phosphorylation of serine 15 is required to maintain basal levels of p21 mRNA. These results provide new evidence for an important function of serine 37 phosphorylation, clearly distinguish the pathways of p53 activation in response to ultraviolet radiation or DNA damage inflicted by adriamycin, and reveal that serine 15 is crucial to support the p53-mediated basal expression of p21.
Bean
L J
LJ
Department of Molecular Biology, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio, OH 44195, USA.
Stark
G R
GR
D000970:Antineoplastic Agents / Q000494:pharmacology; D015152:Blotting, Northern; D002460:Cell Line; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D004317:Doxorubicin / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D005822:Genetic Vectors; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D009154:Mutation; D009687:Nuclear Proteins; D010766:Phosphorylation; D011233:Precipitin Tests; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine / Q000378:metabolism*; D012867:Skin / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism* / Q000528:radiation effects*; D014466:Ultraviolet Rays; D000097642:GADD45 Proteins
D000970:Antineoplastic Agents; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004247:DNA; D017931:DNA Primers; D004317:Doxorubicin; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051736:Proto-Oncogene Proteins c-mdm2; D012694:Serine; D016159:Tumor Suppressor Protein p53; D000097642:GADD45 Proteins; C493956:CDKN1A protein, human; C497206:MDM2 protein, human