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MDM4 (MDMX) localizes at the mitochondria and facilitates the p53‐mediated intrinsic‐apoptotic pathway
Author(s) -
Mancini Francesca,
Di Conza Giusy,
Pellegrino Marsha,
Rinaldo Cinzia,
Prodosmo Andrea,
Giglio Simona,
D'Agnano Igea,
Florenzano Fulvio,
Felicioni Lara,
Buttitta Fiamma,
Marchetti Antonio,
Sacchi Ada,
Pontecorvi Alfredo,
Soddu Silvia,
Moretti Fabiola
Publication year - 2009
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2009.154
Subject(s) - biology , microbiology and biotechnology , mitochondrion , downregulation and upregulation , dna damage , apoptosis , regulator , mdmx , rna interference , transcription (linguistics) , transcription factor , transcriptional regulation , rna , biochemistry , dna , gene , mdm2 , linguistics , philosophy
MDM4 is a key regulator of p53, whose biological activities depend on both transcriptional activity and transcription‐independent mitochondrial functions. MDM4 binds to p53 and blocks its transcriptional activity; however, the main cytoplasmic localization of MDM4 might also imply a regulation of p53‐mitochondrial function. Here, we show that MDM4 stably localizes at the mitochondria, in which it (i) binds BCL2, (ii) facilitates mitochondrial localization of p53 phosphorylated at Ser46 (p53Ser46 P ) and (iii) promotes binding between p53Ser46 P and BCL2, release of cytochrome C and apoptosis. In agreement with these observations, MDM4 reduction by RNA interference increases resistance to DNA‐damage‐induced apoptosis in a p53‐dependent manner and independently of transcription. Consistent with these findings, a significant downregulation of MDM4 expression associates with cisplatin resistance in human ovarian cancers, and MDM4 modulation affects cisplatin sensitivity of ovarian cancer cells. These data define a new localization and function of MDM4 that, by acting as a docking site for p53Ser46 P to BCL2, facilitates the p53‐mediated intrinsic‐apoptotic pathway. Overall, our results point to MDM4 as a double‐faced regulator of p53.