Phosphorylation of p53 on key serines is dispensable for transcriptional activation and apoptosis.
The p53 tumor suppressor is a key mediator of the cellular response to stress. Phosphorylation induced by multiple stress-activated kinases has been proposed to be essential for p53 stabilization, interaction with transcriptional co-activators, and activation of p53 target genes. However, genetic studies suggest that stress-activated phosphorylation may not be essential for p53 activation. We therefore investigated the role of p53 phosphorylation on six key serine residues (Ser(6), Ser(15), Ser(20), Ser(37), Ser(46), and Ser(392)) for p53 activation using nutlin-3, a recently developed small molecule MDM2 antagonist. We show here that nutlin does not induce the phosphorylation of p53. Comparison of the activity of unphosphorylated and phosphorylated p53 induced by the genotoxic drugs doxorubicin and etoposide in HCT116 and RKO cells revealed no difference in their sequence-specific DNA binding and ability to transactivate p53 target genes and to induce p53-dependent apoptosis. We conclude that p53 phosphorylation on six major serine sites is not required for activation of p53 target genes or biological responses in vivo.
Discovery Oncology, Roche Research Center, Hoffmann-La Roche Inc., 340 Kingsland St., Nutley, NJ 07110, USA.
Thelma
T
Thompson
Christian
C
Tovar
Hong
H
Yang
Daisy
D
Carvajal
Binh T
BT
Vu
Qunli
Q
Xu
Geoffrey M
GM
Wahl
David C
DC
Heimbrook
Lyubomir T
LT
Vassilev
D017304:Annexin A5 / Q000494:pharmacology; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004396:Coloring Agents / Q000494:pharmacology; D004247:DNA / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000378:metabolism; D007700:Kinetics; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D010879:Piperazines / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D012694:Serine / Q000737:chemistry; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D017304:Annexin A5; D000903:Antibiotics, Antineoplastic; D000972:Antineoplastic Agents, Phytogenic; D004396:Coloring Agents; D007093:Imidazoles; D009687:Nuclear Proteins; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D012694:Serine; C482205:nutlin 3; D005047:Etoposide; D004317:Doxorubicin; D004247:DNA; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2