Expression of a mRNA related to c-rel and dorsal in early Xenopus laevis embryos.

We describe a Xenopus mRNA, Xrel1, that is related to the avian protooncogene c-rel, the embryonic pattern gene dorsal of Drosophila, and the mammalian transcription factor NK-kappa B/KBF1. The sequence of Xrel1 is homologous to the other rel-related proteins in the large amino-terminal region that defines this class of transcriptional regulators, but the carboxyl-terminal part of the protein is quite different. Xrel1 mRNA is present throughout oogenesis and during early embryogenesis at 4 x 10(5) transcripts per oocyte or embryo. Xrel1 transcripts are present in all of the dissected parts of early embryos that we have examined. They are enriched in the animal hemisphere compared to the vegetal hemisphere of oocytes and blastulae.