Identification of nuclear proteins encoded by viral and cellular myc oncogenes

Abstract

The myelocytomatosis viruses are a family of replication-defective avian retroviruses that cause a variety of tumours in chickens and transform both fibroblasts and macrophages in culture through the activity of their oncogene v-myc¹. A closely related gene (c-myc)^2,3 is found in vertebrate animals and is thought to be the progenitor of v-myc^4,5. Changes in the expression and perhaps the structure of c-myc have been implicated in the genesis of avian^6,7, murine^8–10 and human^11–14 tumours (for a review, see ref. 15). Elucidation of the mechanisms by which v-myc and c-myc might elicit tumorigenesis requires identification of the proteins encoded by these genes. To this end, we have expressed a portion of v-myc in a bacterial host and used the resulting protein to raise antisera that react with myc proteins. We report here that v-myc and c-myc encode closely related proteins with molecular weights (MWs) of ∼58,000. Integration of retroviral DNA near or within c-myc in avian lymphomas^6,7 apparently enhances expression of the gene^6,7. Here we have used cells from one such tumour to identify the protein encoded by c-myc and find that the coding domain for the gene is probably intact.