title: Reciprocal regulation via protein-protein interaction between c-Myc and p21(cip1/waf1/sdi1) in DNA replication and transcription.
abstract: The c-myc protooncogene product (c-Myc) is a transcription factor and is rapidly induced in resting cells following various mitogenic stimuli. c-Myc is thus suggested to play an important role in the transition from quiescence to proliferation. Despite numerous studies, including those on the connection between cyclin E/cyclin-dependent kinase 2 and c-Myc, little has been clarified about c-Myc in terms of the cell cycle regulation. Here we show that c-Myc can directly bind to the carboxyl-terminal region of the cyclin-dependent kinase inhibitor p21(cip1/waf1/sdi1) and thus partially relieves the p21 of the inhibitory effect on DNA synthesis directed by the proliferating cell nuclear antigen-dependent DNA polymerase delta. As for transcription, on the other hand, the p21 binding to the Myc box II region of c-Myc blocks c-Myc-Max complex formation on the E-box and thereby suppresses the transcriptional activation from the E-box by c-Myc. These results suggest that c-Myc activates DNA replication via inactivation of p21 and that p21, vice versa, represses the transcriptional activity of c-Myc. The balance of the reciprocal inactivation between c-Myc and p21 may determine the course of cellular processes such as cell proliferation, differentiation, and apoptosis.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kitaura
authors.forename: M
authors.initials: M
authors.lastname: Shinshi
authors.forename: Y
authors.initials: Y
authors.lastname: Uchikoshi
authors.forename: T
authors.initials: T
authors.lastname: Ono
authors.forename: S M
authors.initials: SM
authors.lastname: Iguchi-Ariga
authors.forename: H
authors.initials: H
authors.lastname: Ariga
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D003001:Cloning, Molecular; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000302:isolation & purification / Q000378:metabolism*; D004261:DNA Replication; D004791:Enzyme Inhibitors / Q000378:metabolism; D004926:Escherichia coli; D016259:Genes, myc; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D018809:Proliferating Cell Nuclear Antigen; D016271:Proto-Oncogene Proteins c-myc; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins