Four sizes of transcript produced by a single sea urchin gene expressed in early embryos

This report concerns a set of sea urchin egg and embryo transcripts complementary to a single-copy region of a cloned DNA fragment (Sp88). Three distinct 16-cell embryo polysomal RNA species were found to hybridize with this fragment. These RNAs are about 1700, 3000, and 4000 nucleotides (nt) in length, and the same species were identified in unfertilized eggs. A significant fraction of all three species of the egg and early embryo transcripts is polyadenylylated. At gastrula stage Sp88 transcripts are almost completely confined to the nucleus [Lev, Z., Thomas, T. L., Lee, A. S., Angerer, R. C., Britten, R. J. & Davidson, E. H. (1980) Dev. Biol, 75, in press]. The Sp88 transcripts of gastrulae are present as a fourth RNA species approximately 5800 nt in length. The four species share a sequence element of cloned DNA fragment that is about 1000 nt long. These RNAs constitute a set of alternative partially overlapping transcripts from the same genomic region.