Greslin A F, Loukin S H, Oka Y, Prescott D M
Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder 80309.
DNA. 1988 Oct;7(8):529-36. doi: 10.1089/dna.1.1988.7.529.
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.
我们已经从多核纤毛虫新奥克特里查（Oxytricha nova）中克隆并测序了一个编码肌动蛋白的1.6kb大核分子。对天然和消化后的大核DNA进行高严谨度的Southern杂交显示，新奥克特里查中只有一个1.6kb的肌动蛋白编码分子。227个核苷酸的5'前导序列包含富含AT的片段，并穿插着短的GC区域。富含AT的区域包含类似TATA的序列。然而，未发现其他已知的真核生物转录调控序列。249个核苷酸的3'尾序列也富含AT，并且不包含任何明显的已知真核生物mRNA加工信号。与密切相关的物种——类新奥克特里查（O. fallax）进行序列比较，结果显示编码区域的序列相似性为87%，而分子的非编码区域几乎完全没有相似性。然而，在这两个物种的肌动蛋白编码分子的非编码区域出现了一些小的序列相似性和基序。新奥克特里查的肌动蛋白编码分子可以编码一个374个氨基酸长的多肽，与一些脊椎动物的细胞质肌动蛋白大小相同。与之前的一份报告相反，我们发现类新奥克特里查的肌动蛋白编码分子也编码一个374个氨基酸长的多肽。
