Revised sequence and expression of cyclin B cDNA from the starfish Asterina pectinifera

Cyclin B cDNA was cloned from the ovary of the starfish Asterina pectinifer a and analyzed by RT-PCR and 3 '- and 5 ' -RACE techniques. The cDNA consis ts of a 0.13-kb upstream untranslated region, a 1.22-kb coding region, and a 0.86-kb downstream untranslated region. The open reading frame encoded a polypeptide of 404 amino acid residues with a calculated molecular weight o f 45,692, All the characteristic sequences, such as destruction and cyclin boxes, cyclin B motif, and cytoplasmic retention and nuclear export signals , were found in the newly cloned cyclin B cDNA, The deduced amino acid sequ ence of the cyclin B cDNA was highly homologous in the middle and carboxy t erminal regions to that from mature eggs of the same organism, but quite di fferent in the amino terminal region, Evidence was obtained which suggested that this cyclin B is expressed in immature and maturing oocytes and is th e same as that cloned from mature eggs.