A mitogen- and anisomycin-stimulated kinase phosphorylates HMG-14 in its basic amino-terminal domain in vivo and on isolated mononucleosomes.
The rapid, transient induction of 80-100 immediate-early (IE) genes upon mitogenic stimulation occurs irrespective of protein synthesis and is mediated by modification of existing proteins. Two mechanisms, not mutually exclusive, involving modification either of sequence-specific transcription factors or of structural chromatin proteins primed by pre-association with responsive effectors are conceivable. Here, we show that upon IE gene induction, the non-histone high-mobility-group protein HMG-14, but not the related protein HMG-17, becomes serine phosphorylated in its basic, amino-terminal region close to where it binds nucleosomal DNA. Phosphorylation, normally transient, occurs independent of transcription and is quantitative and prolonged during superinduction. Brief micrococcal nuclease digestion substantially releases HMG-14 from nuclei in the mononucleosome-bound state. Finally, mononucleosomes prepared from mitogen-stimulated, but not control, cells contain a mitogen-activated kinase that phosphorylates HMG-14 in vitro on the same site(s) as in intact cells. The association of HMG-14 and its mitogen-activated kinase with nuclease-sensitive mononucleosomes has implications for models of mitogen-stimulated IE gene induction.
Barratt
M J
MJ
Nuclear Signalling Laboratory, Randall Institute, King's College London, UK.
Hazzalin
C A
CA
Zhelev
N
N
Mahadevan
L C
LC
D000595:Amino Acid Sequence; D000818:Animals; D000841:Anisomycin / Q000494:pharmacology*; D002460:Cell Line; D004815:Epidermal Growth Factor / Q000494:pharmacology; D017781:Genes, Immediate-Early / Q000187:drug effects*; D006609:High Mobility Group Proteins / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D008836:Micrococcal Nuclease; D008934:Mitogens / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009707:Nucleosomes / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D006609:High Mobility Group Proteins; D008934:Mitogens; D009707:Nucleosomes; D011500:Protein Synthesis Inhibitors; D004815:Epidermal Growth Factor; D000841:Anisomycin; D011494:Protein Kinases; D008836:Micrococcal Nuclease; D013755:Tetradecanoylphorbol Acetate