Requirement for the C-terminal domain of the v-erbA oncogene protein for biological function and transcriptional repression.
In contrast to the normal thyroid hormone receptor, the v-erbA product fails to bind hormone due to mutations in the C-terminal ligand binding domain and thus appears to represent a hormone-independent, oncogenic transcription factor. Therefore, we asked whether or not the C-terminal domain of v-erbA is required for its biological activity and putative transcriptional control functions by analysing mutants with altered C-termini. A v-erbA protein truncated in the C-terminal domain lacked detectable biological activity in transformed erythroblasts and its transcriptional repression function with respect to the band 3 gene was abolished. The protein displayed a nuclear location and could still bind to DNA, indicating that the N-terminal region retained DNA-binding activity but was insufficient to produce characteristic v-erbA changes in erythroblasts. Another biologically defective v-erbA variant with a small frameshift towards the extreme C-terminus also failed to repress band 3, indicating a requirement for a specific C-terminal structure in repression. However, this mutant retained partial biological activity, stimulating erythroblasts to grow at a higher rate than cells containing a completely inactive, deleted v-erbA gene. The results demonstrate that the mutated hormone-binding domain, in addition to the DNA-binding region, is critical for v-erbA biological and transcriptional control functions.
Forrest
D
D
Department of Molecular Biology, Karolinska Institute, Stockholm, Sweden.
Muñoz
A
A
Raynoschek
C
C
Vennström
B
B
Beug
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002455:Cell Division; D002471:Cell Transformation, Neoplastic; D002642:Chick Embryo; D003062:Codon / Q000235:genetics; D005347:Fibroblasts / Q000166:cytology; D005809:Genes, Regulator; D014644:Genetic Variation; D008969:Molecular Sequence Data; D009154:Mutation; D015345:Oligonucleotide Probes; D018774:Oncogene Proteins v-erbA; D009857:Oncogenes; D010957:Plasmids; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D015183:Restriction Mapping; D015682:Retroviridae Proteins, Oncogenic / Q000235:genetics*; D014158:Transcription, Genetic; D014162:Transfection
D003062:Codon; D015345:Oligonucleotide Probes; D018774:Oncogene Proteins v-erbA; D015682:Retroviridae Proteins, Oncogenic; D011505:Protein-Tyrosine Kinases