A subpopulation of the v-erb A oncogene protein, a derivative of a thyroid hormone receptor, associates with heat shock protein 90

The v-erb A oncogene of avian erythroblastosis virus is derived from a host gene for a thyroid hormone receptor and is able to block differentiation of erythroid cells and modify the growth properties of fibroblasts. Unlike its host cell progenitor, the v-erb A protein is found in both cytoplasmic and nuclear fractions of the cell. I report here that the cytoplasmic form of the v-erb A protein is associated in a higher molecular weight complex with heat shock protein 90, the same polypeptide found in association with the unliganded steroid receptors and with the soluble forms of the src oncogene.