title: Targeted destruction of c-Myc by an engineered ubiquitin ligase suppresses cell transformation and tumor formation.
abstract: Given that expression of c-Myc is up-regulated in many human malignancies, targeted inactivation of this oncoprotein is a potentially effective strategy for cancer treatment. The ubiquitin-proteasome pathway of protein degradation is highly specific and can be engineered to achieve the elimination of undesirable proteins such as oncogene products. We have now generated a fusion protein (designated Max-U) that is composed both of Max, which forms a heterodimer with c-Myc, and of CHIP, which is a U box-type ubiquitin ligase (E3). Max-U physically interacted with c-Myc in transfected cells and promoted the ubiquitylation of c-Myc in vitro. It also reduced the stability of c-Myc in vivo, resulting in suppression of transcriptional activity dependent on c-Myc. Expression of Max-U reduced both the abundance of endogenous c-Myc in and the proliferation rate of a Burkitt lymphoma cell line. Furthermore, expression of Max-U but not that of a catalytically inactive mutant thereof markedly inhibited both the anchorage-independent growth in vitro of NIH 3T3 cells that overexpress c-Myc as well as tumor formation by these cells in nude mice. These findings indicate that the targeted destruction of c-Myc by an artificial E3 may represent an effective therapeutic strategy for certain human malignancies.
authors.affiliation: Department of Molecular Biochemistry, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Shigetsugu
authors.initials: S
authors.lastname: Hatakeyama
authors.forename: Masashi
authors.initials: M
authors.lastname: Watanabe
authors.forename: Yo
authors.initials: Y
authors.lastname: Fujii
authors.forename: Keiichi I
authors.initials: KI
authors.lastname: Nakayama
mesh_terms: D000818:Animals; D002051:Burkitt Lymphoma / Q000235:genetics / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D041681:NIH 3T3 Cells; D015202:Protein Engineering; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; D011993:Recombinant Fusion Proteins; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases