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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 589

Greslin, A.F., Loukin, S.H., Oka, Y., and Prescott, D.M.; An analysis of the macronuclear actin genes of Oxytricha. DNA 7:529-536, 1988

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We have cloned and sequenced a 1.6-kb macronuclear molecule encoding actin from the hypotrichous ciliate Oxytricha nova. High-stringency Southern hybridization to native and digested macronuclear DNA shows that there is only one 1.6-kb actin-encoding molecule in O. nova. The 227-nucleotide 5' leader sequence contains AT-rich stretches punctuated by short GC regions. The AT-rich regions contain TATA-like sequences. However, other known eukaryote transcription regulatory sequences were not found. The 249-nucleotide 3' trailer sequence is also AT-rich and does not contain any obvious known eukaryotic mRNA processing signals. Sequence comparison with a closely related species, O. fallax, shows an 87% sequence similarity in the coding regions and an almost total lack of similarity in the noncoding regions of the molecules. However, a few small sequence similarities and motifs appear in the noncoding regions of the actin-encoding molecules of these two species. The actin-encoding molecule of O. nova could encode a polypeptide 374 amino acids long, the same size as some vertebrate cytoplasmic actins. Contrary to a previous report, we show that the actin-encoding molecule of O. fallax also codes for a polypeptide 374 amino acids long.