Human epidermal growth factor receptor cDNA is homologous to a variety of RNAs overproduced in A431 carcinoma cells

Abstract

The recently discovered similarity between the human epidermal growth factor (EGF) receptor and the avian erythroblastosis virus v-erb-B protein1 supports the hypothesis that viral oncogenes share a common evolutionary origin with genes encoding growth-regulating cell-surface receptors. To elucidate the relationship between receptors and malignant transformation, we have now used a fragment of v-erb-B as a probe to screen a cDNA library of mRNA from A431 human carcinoma cells, which possess a large number of EGF receptors2. Of the six clones isolated, the largest (pE7) contains an insert of 2.4 kilobase pairs (kbp) whose deduced amino acid sequence is homologous to the v-erb-B protein and identical to reported EGF receptor peptide sequences1. This pE7 cDNA hybridized to three prominent RNAs of ∼10, 5.6 and 2.9 kilobases (kb), and to three minor species of 6.3, 4.6 and 3.3 kb. All were present in elevated levels in A431 cells. The prominent 2.9-kb RNA was homologous only to the 5′ portion of the pE7 insert. This result raises the possibility that differential RNA processing is used by A431 cells to generate a variety of RNAs.