Enhanced Mdm2 activity inhibits pRB function via ubiquitin-dependent degradation

Chiharu Uchida; Seiichi Miwa; Kyoko Kitagawa; Takayuki Hattori; Tomoyasu Isobe; Sunao Otani; Toshiaki Oda; Haruhiko Sugimura; Takehiko Kamijo; Keizou Ookawa; Hideyo Yasuda; Masatoshi Kitagawa

doi:10.1038/sj.emboj.7600486

Enhanced Mdm2 activity inhibits pRB function via ubiquitin-dependent degradation

EMBO J. 2005 Jan 12;24(1):160-9. doi: 10.1038/sj.emboj.7600486. Epub 2004 Dec 2.

Authors

Chiharu Uchida¹, Seiichi Miwa, Kyoko Kitagawa, Takayuki Hattori, Tomoyasu Isobe, Sunao Otani, Toshiaki Oda, Haruhiko Sugimura, Takehiko Kamijo, Keizou Ookawa, Hideyo Yasuda, Masatoshi Kitagawa

Affiliation

¹ Department of Biochemistry 1, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan.

Abstract

Retinoblastoma gene product (pRB) plays critical roles in regulation of the cell cycle and tumor suppression. It is known that downregulation of pRB can stimulate carcinogenesis via abrogation of the pRB pathway, although the mechanism has not been elucidated. In this study, we found that Mdm2, a ubiquitin ligase for p53, promoted ubiquitin-dependent degradation of pRB. pRB was efficiently ubiquitinated by wild-type Mdm2 in vivo as well as in vitro, but other RB family proteins were not. Mutant Mdm2 with a substitution in the RING finger domain showed dominant-negative stabilization of pRB. Both knockout and knockdown of Mdm2 caused accumulation of pRB. Moreover, Mdm2 inhibited pRB-mediated flat formation of Saos-2 cells. Downregulation of pRB expression was correlated with a high level of expression of Mdm2 in human lung cancers. These results suggest that Mdm2 regulates function of pRB via ubiquitin-dependent degradation of pRB.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Carcinoma, Non-Small-Cell Lung / metabolism
Carcinoma, Non-Small-Cell Lung / pathology
Cell Line
Cell Shape
Humans
Lung Neoplasms / metabolism
Lung Neoplasms / pathology
Mice
Nuclear Proteins / genetics
Nuclear Proteins / metabolism*
Proto-Oncogene Proteins / genetics
Proto-Oncogene Proteins / metabolism*
Proto-Oncogene Proteins c-mdm2
RNA, Small Interfering / genetics
RNA, Small Interfering / metabolism
Recombinant Fusion Proteins / genetics
Recombinant Fusion Proteins / metabolism
Retinoblastoma Protein / genetics
Retinoblastoma Protein / metabolism*
Signal Transduction / physiology
Tumor Suppressor Protein p14ARF / metabolism
Tumor Suppressor Protein p53 / genetics
Tumor Suppressor Protein p53 / metabolism
Ubiquitins / metabolism*

Substances

Nuclear Proteins
Proto-Oncogene Proteins
RNA, Small Interfering
Recombinant Fusion Proteins
Retinoblastoma Protein
Tumor Suppressor Protein p14ARF
Tumor Suppressor Protein p53
Ubiquitins
MDM2 protein, human
Mdm2 protein, mouse
Proto-Oncogene Proteins c-mdm2