PARAMECIUM-TETRAURELIA ENCODES UNCONVENTIONAL ACTIN CONTAINING SHORT INTRONS

The polymerase chain reaction was used to amplify and clone an actin g ene fragment from Paramecium tetraurelia. This DNA fragment was 1.138 bp long, more than 96% of the actin coding sequence, and contained fou r in-frame UAA codons and two small introns located at positions uniqu e in the actin intron catalogue. This is the first report for the phyl um Ciliophora of an actin gene containing introns. The deduced amino a cid sequence of this actin fragment shared 58-77% identity with other actins. When compared with rabbit alpha-muscle actin, similarities wer e observed mainly in subdomains 1 and 3, whereas subdomains 2 and 4 ap peared to be more divergent.