title: p19ARF directly and differentially controls the functions of c-Myc independently of p53.
abstract: Increased expression of the oncogenic transcription factor c-Myc causes unregulated cell cycle progression. c-Myc can also cause apoptosis, but it is not known whether the activation and/or repression of c-Myc target genes mediates these diverse functions of c-Myc. Because unchecked cell cycle progression leads to hyperproliferation and tumorigenesis, it is essential for tumour suppressors, such as p53 and p19ARF (ARF), to curb cell cycle progression in response to increased c-Myc (refs 2, 3). Increased c-Myc has previously been shown to induce ARF expression, which leads to cell cycle arrest or apoptosis through the activation of p53 (ref. 4). Here we show that ARF can inhibit c-Myc by a unique and direct mechanism that is independent of p53. When c-Myc increases, ARF binds with c-Myc and dramatically blocks c-Myc's ability to activate transcription and induce hyperproliferation and transformation. In contrast, c-Myc's ability to repress transcription is unaffected by ARF and c-Myc-mediated apoptosis is enhanced. These differential effects of ARF on c-Myc function suggest that separate molecular mechanisms mediate c-Myc-induced hyperproliferation and apoptosis. This direct feedback mechanism represents a p53-independent checkpoint to prevent c-Myc-mediated tumorigenesis.
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2175, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Qi
authors.forename: Mark A
authors.initials: MA
authors.lastname: Gregory
authors.forename: Zhaoliang
authors.initials: Z
authors.lastname: Li
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Brousal
authors.forename: Kimberly
authors.initials: K
authors.lastname: West
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Hann
mesh_terms: D000818:Animals; D017209:Apoptosis; D002453:Cell Cycle; D002455:Cell Division; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D019941:Cyclin-Dependent Kinase Inhibitor p16; D017353:Gene Deletion; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D011233:Precipitin Tests; D011485:Protein Binding; D016271:Proto-Oncogene Proteins c-myc / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D014158:Transcription, Genetic; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: C417743:Cdkn2a protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016271:Proto-Oncogene Proteins c-myc; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53