Myc and Max associate in vivo.
Max is a helix-loop-helix zipper protein that associates in vitro with Myc family proteins to form a sequence-specific DNA-binding complex. We show here, by means of a coimmunoprecipitation assay with anti-Myc and anti-Max antibodies, that Myc and Max are associated in vivo and essentially all of the newly synthesized Myc can be detected in a complex with Max. This complex possesses specific DNA-binding activity for CACGTG-containing oligonucleotides. Although Max itself is a highly stable protein, Myc is rapidly degraded during or after its association with Max. In vivo Max is shown to be a nuclear protein phosphorylated by casein kinase II, and alternatively spliced forms of Max are expressed in cells. Furthermore, the levels of Max expression are equivalent in quiescent, mitogen-stimulated, and cycling cells. We conclude that the highly regulated rate of Myc biosynthesis is likely to be a limiting step in the formation of Myc:Max complexes.
Blackwood
E M
EM
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
Lüscher
B
B
Eisenman
R N
RN
D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites / Q000235:genetics; D047388:Casein Kinases; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015870:Gene Expression; D046911:Macromolecular Substances; D009687:Nuclear Proteins / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides / Q000235:genetics / Q000378:metabolism; D010449:Peptide Mapping; D010766:Phosphorylation; D011233:Precipitin Tests; D011494:Protein Kinases / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014157:Transcription Factors; D014407:Tumor Cells, Cultured
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; C067850:Myc associated factor X; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D016271:Proto-Oncogene Proteins c-myc; D011994:Recombinant Proteins; D014157:Transcription Factors; D011494:Protein Kinases; D047388:Casein Kinases