title: c-Jun-NH2 kinase (JNK) contributes to the regulation of c-Myc protein stability.
abstract: In accord with the central role c-Myc plays in control of cell growth and death, the stability of this protein is tightly regulated. Although the NH2-terminal domain of c-Myc has been implicated in the regulation of its stability, c-Myc-S, which lacks this domain, is equally unstable, pointing to the role of additional domains in the regulation of c-Myc stability. Our former studies revealed that amino acids (aa) 127-189 of c-Myc are responsible for stress-induced stability of the c-Myc protein. This region of c-Myc shares homology with the delta domain of c-Jun, which is required for JNK association and subsequent targeting of c-Jun for ubiquitination under non-stressed growth conditions. Here we demonstrate that JNK associates with, and mediates, c-Myc ubiquitination and degradation. Addition of JNK increased the degree of c-Myc ubiquitination in in vitro ubiquitination reactions. Increased c-Myc stability following MEKK1/JNK stimuli is abolished upon mutation within the delta-like domain of c-Myc (aa 166-181), as well as deletion of aa 127-189. Significantly, inhibition of JNK expression via small interfering RNA increased c-Myc protein expression. Similarly, squelching JNK association with c-Myc by overexpression of a peptide corresponding to aa 127-189 of c-Myc increased endogenous c-Myc stability and elevated the fraction of cells within the G2/M phase of the cell cycle. In all, these findings point to the contribution of JNK to the regulation of c-Myc protein stability under normal growth conditions.
authors: Ruttenberg Cancer Center, Mount Sinai School of Medicine, New York, New York 10029, USA.
authors: Dania
authors: D
authors: Alarcon-Vargas
authors: Ze'ev
authors: Z
authors: Ronai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D004355:Drug Stability; D015870:Gene Expression; D016259:Genes, myc; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D048031:JNK Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D041681:NIH 3T3 Cells; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D016271:Proto-Oncogene Proteins c-myc / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D016271:Proto-Oncogene Proteins c-myc; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D025801:Ubiquitin; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases; C482576:MAP3K1 protein, human; C482578:Map3k1 protein, mouse