title: Time-dependent activation of Phox2a by the cyclic AMP pathway modulates onset and duration of p27Kip1 transcription.
abstract: In noradrenergic progenitors, Phox2a mediates cell cycle exit and neuronal differentiation by inducing p27(Kip1) transcription in response to activation of the cyclic AMP (cAMP) pathway. The mechanism of cAMP-mediated activation of Phox2a is unknown. We identified a cluster of phosphoserine-proline sites in Phox2a by mass spectrometry. Ser206 appeared to be the most prominent phosphorylation site. A phospho-Ser206 Phox2a antibody detected dephosphorylation of Phox2a that was dependent on activation of the cAMP pathway, which occurred prior to neuronal differentiation of noradrenergic CAD cells. Employing serine-to-alanine and serine-to-aspartic acid Phox2a substitution mutants expressed in inducible CAD cell lines, we demonstrated that the transcriptional activity of Phox2a is regulated by two sequential cAMP-dependent events: first, cAMP signaling promotes dephosphorylation of Phox2a in at least one site, Ser206, thereby allowing Phox2a to bind DNA and initiate p27(Kip1) transcription; second, following dephosphorylation of the phosphoserine cluster (Ser202 and Ser208), Phox2a becomes phosphorylated by protein kinase A (PKA) on Ser153, which prevents association of Phox2a with DNA and terminates p27(Kip1) transcription. This represents a novel mechanism by which the same stimulus, cAMP signaling, first activates Phox2a by dephosphorylation of Ser206 and then, after a built-in delay, inactivates Phox2a via PKA-dependent phosphorylation of Ser153, thereby modulating onset and duration of p27(Kip1) transcription.
authors: Department of Basic Medical Sciences, Purdue University, West Lafayette, IN 47907-2026, USA.
authors: Min Hwa
authors: MH
authors: Shin
authors: Nirmala
authors: N
authors: Mavila
authors: Wen-Horng
authors: WH
authors: Wang
authors: Sasha
authors: S
authors: Vega Alvarez
authors: Mark C
authors: MC
authors: Hall
authors: Ourania M
authors: OM
authors: Andrisani
mesh_terms: D000409:Alanine / Q000235:genetics; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002454:Cell Differentiation; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics* / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007381:Intermediate Filament Proteins / Q000378:metabolism; D013058:Mass Spectrometry; D008562:Membrane Glycoproteins / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D064531:Peripherins; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014158:Transcription, Genetic
chemical_list: D018398:Homeodomain Proteins; D007381:Intermediate Filament Proteins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D064531:Peripherins; D012333:RNA, Messenger; D050760:Cyclin-Dependent Kinase Inhibitor p27; D010768:Phosphoserine; D004247:DNA; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000409:Alanine