Identification of two translational products for c-myb.

The c-myb gene is the normal cellular homolog of v-myb, the oncogenic component of Avian Myeloblastosis Virus (AMV). The c-myb gene has previously been shown to code for a single protein species of about 75 kd. However, accumulating evidence indicates that this gene could code for multiple mRNAs as a result of differential splicing. This was first detected in the ABPL-2 tumor line and was later shown to occur in normal cells. To test if indeed these differentially spliced mRNAs code for a new protein species that went hitherto undetected, a series of antibodies directed against specific domains of the myb protein, including the putative sequences that could be generated from the alternatively spliced mRNAs were generated. Immunoprecipitation analysis using these antibodies show that both normal and tumor cell lines synthesize at least two myb proteins, one of 75 kd and the other of 89 kd.