Regulation of Hypoxia-Inducible mRNAs by the von Hippel-Lindau Tumor Suppressor Protein Requires Binding to Complexes Containing Elongins B/C and Cul2

Abstract

The von Hippel-Lindau tumor suppressor protein (pVHL) binds to elongins B and C and posttranscriptionally regulates the accumulation of hypoxia-inducible mRNAs under normoxic (21% O 2 ) conditions. Here we report that pVHL binds, via elongin C, to the human homolog of the Caenorhabditis elegans Cul2 protein.Coimmunoprecipitation and chromatographic copurification data suggest that pVHL-Cul2 complexes exist in native cells. pVHL mutants that were unable to bind to complexes containing elongin C and Cul2 were likewise unable to inhibit the accumulation of hypoxia-inducible mRNAs. A model for the regulation of hypoxiainducible mRNAs by pVHL is presented based on the apparent similarity of elongin C and Cul2 to Skp1 and Cdc53, respectively. These latter proteins form complexes that target specific proteins for ubiquitin-dependent proteolysis.

Alternate choice of initiation codon produces a biologically active product of the von Hippel Lindau gene with tumor suppressor activity

“…pVHL30 has been shown previously to bind to at least four cellular proteins, elongin B, elongin C, Hs-CUL2, and ®bronectin (Duan et al, 1995a;Pause et al, 1997;Lonergan et al, 1998;Ohh et al, 1998). To test whether pVHL18 retains similar functions, 786-0 transgenic subclones transfected expressing pVHL25 or pVHL18 were metabolically labeled with 35 S-methionine, and lysates immunoprecipitated with IG32 monoclonal antibody.…”

“…Certain, but not all, tumor-derived mutants of pVHL are defective in binding to the B/C complex (Duan et al, 1995b;Kishida et al, 1995;Kibel et al, 1995). In addition, wild-type pVHL appears to interact with the human Hs-CUL2 protein (Pause et al, 1997;Lonergan et al, 1998), a member of a conserved gene family believed to play a role in ubiquitin-mediated protein degradation and growth control in lower eukaryotes. Binding of pVHL to HS-CUL2 appears to be dependent on binding of pVHL to elongin B/C , suggesting that the pVHL/B/C/Hs-CUL2 complex may a ect ubiquitination of target proteins regulating tumorigenic growth.…”

“…Biochemical studies have shown that interaction of pVHL with elongin B, elongin C and Hs-CUL2 require an intact C-terminus of pVHL Lonergan et al, 1998;Kishida et al, 1995). The role of the characteristic acidic N-terminus of pVHL, containing eight repeats of the Gly-X-Glu-Glu-X motif, in tumor suppression is so far unclear.…”

Hipoxia tumoral. Papel del factor inducible por hipoxia

“…Hay 2 locales de señalización nuclear (NLS), situados en el C-terminal (aminoácidos 718-721) y en el N-terminal (aminoácidos [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33], pero sólo el C-terminal es el responsable por la acumulación nuclear del HIF-1α 16 . Además, se sabe que el HIF contiene 2 dominios de transactivación (TAD) en el C-terminal (aminoácidos 531-575 y 786-826), que están separados por una secuencia de aminoácidos (575-786) que inhiben la transactivación 17 ( fig.…”

“…En el dominio de la degradación oxígeno-dependiente (ODD) del HIF-1α, los residuos de prolina en las posiciones 402 y 564 tienen un importante impacto en la estabilidad de la proteína en condiciones de normoxia, pues permiten, cuando están hidroxiladas, el reconocimiento por la proteína Von Hippel Lindau (pVHL) y la posterior activación de la vía de degradación de la ubiquitina [20][21][22][23][24][25] . La hidroxilación de los residuos de prolina en el ODD del HIF-1α representa el punto crítico que regula la estabilidad de la proteína 26,27 ( fig.…”