title: Mnt-Max to Myc-Max complex switching regulates cell cycle entry.
abstract: The c-Myc oncoprotein is strongly induced during the G0 to S-phase transition and is an important regulator of cell cycle entry. In contrast to c-Myc, the putative Myc antagonist Mnt is maintained at a constant level during cell cycle entry. Mnt and Myc require interaction with Max for specific DNA binding at E-box sites, but have opposing transcriptional activities. Here, we show that c-Myc induction during cell cycle entry leads to a transient decrease in Mnt-Max complexes and a transient switch in the ratio of Mnt-Max to c-Myc-Max on shared target genes. Mnt overexpression suppressed cell cycle entry and cell proliferation, suggesting that the ratio of Mnt-Max to c-Myc-Max is critical for cell cycle entry. Furthermore, simultaneous Cre-Lox mediated deletion of Mnt and c-Myc in mouse embryo fibroblasts rescued the cell cycle entry and proliferative block caused by c-Myc ablation alone. These results demonstrate that Mnt-Myc antagonism plays a fundamental role in regulating cell cycle entry and proliferation.
authors.affiliation: Shriners Hospitals for Children, Portland, OR 97201, USA.
authors.forename: William
authors.initials: W
authors.lastname: Walker
authors.forename: Zi-Qiang
authors.initials: ZQ
authors.lastname: Zhou
authors.forename: Sara
authors.initials: S
authors.lastname: Ota
authors.forename: Anthony
authors.initials: A
authors.lastname: Wynshaw-Boris
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hurlin
mesh_terms: D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D050976:Basic-Leucine Zipper Transcription Factors; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002461:Cell Line, Transformed; D049109:Cell Proliferation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000502:physiology; D005347:Fibroblasts / Q000378:metabolism; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000502:physiology; D020868:Gene Silencing / Q000502:physiology; D018390:Gene Targeting; D046911:Macromolecular Substances / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D050976:Basic-Leucine Zipper Transcription Factors; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; C484561:Mnt protein, mouse; C067850:Myc associated factor X; C489428:Myc protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D012097:Repressor Proteins; D014157:Transcription Factors; C068422:Max protein, mouse