1. PKA, PKC, and the protein phosphatase 2A influence HAND factor function: a mechanism for tissue-specific transcriptional regulation.
- Author
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Firulli BA, Howard MJ, McDaid JR, McIlreavey L, Dionne KM, Centonze VE, Cserjesi P, Virshup DM, and Firulli AB
- Subjects
- Amino Acid Sequence, Animals, Basic Helix-Loop-Helix Transcription Factors, Cell Differentiation physiology, Cell Line, Chick Embryo, DNA-Binding Proteins genetics, Dimerization, Genes, Reporter, Helix-Loop-Helix Motifs, Humans, Molecular Sequence Data, Morphogenesis physiology, Phosphoprotein Phosphatases genetics, Phosphorylation, Protein Phosphatase 2, Recombinant Fusion Proteins genetics, Recombinant Fusion Proteins metabolism, Sequence Alignment, Stem Cells physiology, Transcription Factors genetics, Two-Hybrid System Techniques, Zebrafish Proteins, Cyclic AMP-Dependent Protein Kinases metabolism, DNA-Binding Proteins metabolism, Gene Expression Regulation, Developmental, Phosphoprotein Phosphatases metabolism, Protein Kinase C metabolism, Protein Subunits metabolism, Transcription Factors metabolism, Transcription, Genetic
- Abstract
The bHLH factors HAND1 and HAND2 are required for heart, vascular, neuronal, limb, and extraembryonic development. Unlike most bHLH proteins, HAND factors exhibit promiscuous dimerization properties. We report that phosphorylation/dephosphorylation via PKA, PKC, and a specific heterotrimeric protein phosphatase 2A (PP2A) modulates HAND function. The PP2A targeting-subunit B56delta specifically interacts with HAND1 and -2, but not other bHLH proteins. PKA and PKC phosphorylate HAND proteins in vivo, and only B56delta-containing PP2A complexes reduce levels of HAND1 phosphorylation. During RCHOI trophoblast stem cell differentiation, B56delta expression is downregulated and HAND1 phosphorylation increases. Mutations in phosphorylated residues result in altered HAND1 dimerization and biological function. Taken together, these results suggest that site-specific phosphorylation regulates HAND factor functional specificity.
- Published
- 2003
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