The 3' Untranslated Region of mRNAs from the Ciliate Nyctotherus ovalis

The 3' untranslated regions (3'UTRs) of cDNAs from Nyctotherus ovalis, a ciliate from the digestive tract of cockroaches, were examined for their sequence composition. All 3' sequences studied here were characteristically short - generally having around 20 to 30 nucleotides between the stop codon and the first nucleotide of the polyA tail. The stop codon used in all sequences studied was UAA, which although one of the "universal" stop codons, is often used to encode glutamine in other ciliates such as Tetrahymena. The polyadenylation signal used in N. ovalis could not be determined from the sequence information, but it is clearly not the `universal' AAUAAA signal. Furthermore, in messages encoding cathepsin B the 3'UTRs were of variable length, with the position where polyadenylation was initiated varying - despite a high conservation of the coding part of the message.