We characterized the proto-oncogene ets-2 homolog isolated from a Xenopus laevis oocyte CDNA library. The open-reading frame length of the ets-2 sequence is 472 amino acids. The putative initiation and termination codons are co-linear with the homologous human and mouse sequences. The entire CDNA sequence was cloned into the bacterial-expression vector, pJL6, and high-level 'expression of a non-fusion proto-oncogene encoded protein was obtained. The ets-2 expressed protein is being purified to make antiserum and to study its biochemical properties. The expression pattern of a 3.2 kb proto-oncogene ets-2 MRNA is typical of a maternal MRNA during oogenesis and embryonic development. The MRNA level (on an oocyte/embryo basis) remains almost constant during oogenesis, and a similar level is maintained from the egg stage through early cleavage. The ets-2 MRNA was found to be nearly evenly distributed throughout the cytoplasm of the oocytes, and not specifically localized in the animal or vegetal pole. Injection of antisense oligonucleotides into oocytes results in the degradation of the endogenous ets-2 MRNA and blocks germinal vesicle breakdown (GVBD) induced by hormone. Thus, the ets-2 product appears to be required for the meiotic maturation of Xenopus oocytes.
