REQUIREMENT FOR THE C-TERMINAL DOMAIN OF THE V-ERBA ONCOGENE PROTEIN FOR BIOLOGICAL FUNCTION AND TRANSCRIPTIONAL REPRESSION

1 March 1990

journal article
research article

Vol. 5 (3) , 309-316

Abstract

In contrast to the normal thyroid hormone receptor, the v-erb A 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 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 characteristics 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 biololgical 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 region, is critical for v-erbA biological and transcriptional control functions.

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