Phosphorylation of the v-erbA protein is required for its function as an oncogene
| Autor: | C Glineur, J Ghysdael, Hartmut Beug, Martin Zenke |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
Gene Expression Regulation
Viral Erythrocytes animal structures Erythroblasts medicine.drug_class Immunoprecipitation Molecular Sequence Data Retroviridae Proteins Oncogenic Gene Products gag Chick Embryo Alpharetrovirus Piperazines 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine Genetics medicine Animals Protein phosphorylation Amino Acid Sequence Phosphorylation Protein Kinase Inhibitors Band 3 Protein kinase C Base Sequence biology Cell Differentiation Oncogenes Oncogene Proteins v-erbA Protein kinase inhibitor Isoquinolines Fusion protein Molecular biology Phenotype Mutagenesis Site-Directed biology.protein Signal transduction Developmental Biology |
| Zdroj: | Genes & Development. 4:1663-1676 |
| ISSN: | 1549-5477 0890-9369 |
| DOI: | 10.1101/gad.4.10.1663 |
| Popis: | The v-erbA oncogene of avian erythroblastosis virus (AEV) encodes a ligand-independent mutated version of the chicken c-erbA alpha-encoded thyroid hormone receptor. The v-erbA gene product, a 75-kD gag/v-erbA fusion protein, is phosphorylated on Ser-16/17 of its v-erbA-encoded domain, and phosphorylation at this site is increased in vivo after activation of either the PKA or PKC signal transduction pathways. To test the hypothesis that phosphorylation of Ser-16/17 regulates gag/v-erbA protein function, mutant proteins in which Ser-16/17 had been changed to alanine or threonine residues were analyzed for their ability to inhibit erythroid differentiation of ts v-erbB or ts v-sea-transformed erythroblasts at nonpermissive temperature. Conversion of Ser-16/17 into alanine, although not affecting nuclear localization or DNA binding of the gag/erbA protein, prevented phosphorylation of the v-erbA-encoded domain of the protein both in unstimulated cells or after stimulation by PKA and PKC activators. The nonphosphorylatable AA-gag/v-erbA protein proved unable to inhibit temperature-induced differentiation of ts v-erbB and ts v-sea-transformed erythroblasts and to block expression of the erythrocyte-specific genes band 3 and carbonic anhydrase II. Back mutation of these alanine residues to serine resulted in the recovery of both normal phosphorylation levels and wild-type biological activity. In contrast, substitution of Ser-16/17 for threonine, which preserved phosphorylation in unstimulated cells but not PKA- and PKC-enhanced phosphorylation, resulted in a partially active gag/v-erbA protein. These results, together with the fact that the protein kinase inhibitor H7 resulted in both a dose-dependent inhibition of gag/v-erbA protein phosphorylation and the induction of terminal differentiation of AEV-transformed erythroblasts show that phosphorylation of gag/v-erbA protein is required for full biological activity. These results support the hypothesis that phosphorylation of the gag/v-erbA protein is important for transcriptional repression of at least some of its target genes in erythroid cells. |
| Databáze: | OpenAIRE |
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