Voi. 134, No. 2, 1986 January 29, 1986 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 7]5-722 IDENTIFICATION OF THE V-REL PROTEIN IN REV-T TRANSFORMED CHICKEN BONE MARROW CELLS AND EXPRESSION IN COSI CELLS Kenneth Garson and C. Yong Kang Department of Microbiology and Immunology, University of Ottawa, School of Medicine, Ottawa, Ontario, Canada KIH 8M5 Received December 4, 1985 The product of the v-rel oncogene has been identified as a 55,000 dalton protein using antiserum prepared against a synthetic polypeptide whose sequence was deduced from the DNA sequence of v-rel. This antiserum was used in a Western blot assay to identify the product of v-rel in chicken bone marrow cells transformed with reticuloendotheliosis virus, strain T (REV-T), and in Cosl cells transfected with an expression vector containing the v- rel gene. Transient expression of v-rel under the transcriptional control of the SV~0 late promoter in Cosl cells leads to the synthesis of a rel specific protein with a similar molecular weight. ® 1986 Academic Press, Inc. Great effort has been expended in identifying the products of viral oncogenes and characterizing their biochemical properties (l-3). Unfortunately, with the tyrosine kinase family of oncogene products, the identification of numerous substrates makes it difficult to differentiate between iortuitous substrates and those important in the pathway to cell transformation (~-9). The characterization of more oncogene products may help to identify some of these important pathways. We chose to study the v-rel oncogene carried by reticuloendotheliosis virus strain T (REV-T), a highly oncogenic defective avian retrovirus. V-tel has one major open reading frame with a capacity to code for a protein of 503 amino acids (10, l t). The open reading frame initiates with the putative env gene initiation codon, 37 nucleotides 5' of the start of the cell derived sequences and terminates approximately 57 nucleotides 3' of the cell derived sequences in an alternate reading frame of the env gene (10, ll). The putative product would be an (env)-(v-rel)-(out of frame env) fusion polypeptide. Based on DNA and deduced amino acid sequence data, v-re[ has not been shown to be closely related to any other viral oncogene (i 1), although the possibility of a distant relatedness to v-src has been discussed (10). Although v-rel has been cloned (12) and sequenced (10, ll), there has been no published report to date identifying the 0006-291X/86 $1.50 Copyright © 1986 by Academic Press, Inc. All rights of reproduction in any form reserved. 716