Targeted inactivation of Mdm2 RING finger E3 ubiquitin ligase activity in the mouse reveals mechanistic insights into p53 regulation.
It is believed that Mdm2 suppresses p53 in two ways: transcriptional inhibition by direct binding, and degradation via its E3 ligase activity. To study these functions physiologically, we generated mice bearing a single-residue substitution (C462A) abolishing the E3 function without affecting p53 binding. Unexpectedly, homozygous mutant mice died before E7.5, and deletion of p53 rescued the lethality. Furthermore, reintroducing a switchable p53 by crossing with p53ER(TAM) mice surprisingly demonstrated that the mutant Mdm2(C462A) was rapidly degraded in a manner indistinguishable from that of the wild-type Mdm2. Hence, our data indicate that (1) the Mdm2-p53 physical interaction, without Mdm2-mediated p53 ubiquitination, cannot control p53 activity sufficiently to allow early mouse embryonic development, and (2) Mdm2's E3 function is not required for Mdm2 degradation.
Itahana
Koji
K
Department of Radiation Oncology, School of Medicine, the University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7512, USA.
Mao
Hua
H
Jin
Aiwen
A
Itahana
Yoko
Y
Clegg
Hilary V
HV
Lindström
Mikael S
MS
Bhat
Krishna P
KP
Godfrey
Virginia L
VL
Evan
Gerard I
GI
Zhang
Yanping
Y
D019943:Amino Acid Substitution; D000818:Animals; D002478:Cells, Cultured; D004249:DNA Damage; D015536:Down-Regulation; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism / Q000528:radiation effects; D005720:Gamma Rays; D018507:Gene Expression Regulation, Developmental / Q000528:radiation effects; D005838:Genotype; D005865:Gestational Age; D006720:Homozygote; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010641:Phenotype; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017434:Protein Structure, Tertiary; D051736:Proto-Oncogene Proteins c-mdm2 / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
D016159:Tumor Suppressor Protein p53; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; D046988:Proteasome Endopeptidase Complex