Kusakabe T, Makabe K W, Satoh N
Department of Zoology, Faculty of Science, Kyoto University, Japan.
J Mol Biol. 1992 Oct 5;227(3):955-60. doi: 10.1016/0022-2836(92)90237-e.
We have isolated and determined the complete nucleotide sequences of two genes, HrMA4a and HrMA2, which encode the same muscle actin protein of the tunicate Halocynthia roretzi. HrMA4a and HrMA2 contain three exons, and the genes have intron-exon splice junctions at the same positions. The 5' flanking region of HrMA4a gene contains several potential regulatory elements. A TATA box is located at -30 and a CArG box found in regulatory region of vertebrate muscle-specific genes is located at -116. Seven E-box consensus sequences (CANNTG) known as binding sites for vertebrate myogenic determination factors are found within a 500 base-pair portion of the 5' flanking region of HrMA4a gene. HrMA4a and HrMA2 are separated by 1600 bases in genomic DNA and transcribed in the same direction. In addition to these genes, we have identified three other actin genes encoding muscle-type actins. All five actin genes are located in a 30 x 10(3) base-pair region of the genome and aligned in the same direction. This is the first report of a cluster of "vertebrate-type" muscle actin genes. The consensus sequences of 5' flanking region are conserved among these five genes, suggesting that the expression of the genes is controlled coordinately. This may be advantageous for the accumulation of considerable amounts of actin proteins in rapidly developing embryos of this animal.
我们已经分离并确定了两个基因HrMA4a和HrMA2的完整核苷酸序列，它们编码海鞘柄海鞘（Halocynthia roretzi）的同一种肌肉肌动蛋白。HrMA4a和HrMA2包含三个外显子，并且这些基因在相同位置具有内含子-外显子剪接连接。HrMA4a基因的5'侧翼区域包含几个潜在的调控元件。一个TATA框位于-30处，在脊椎动物肌肉特异性基因调控区域中发现的一个CArG框位于-116处。在HrMA4a基因5'侧翼区域的500个碱基对部分内发现了七个E框共有序列（CANNTG），它们是脊椎动物生肌决定因子的结合位点。HrMA4a和HrMA2在基因组DNA中相隔1600个碱基，并以相同方向转录。除了这些基因，我们还鉴定出另外三个编码肌肉型肌动蛋白的肌动蛋白基因。所有五个肌动蛋白基因都位于基因组的一个30×10³碱基对区域内，并以相同方向排列。这是关于“脊椎动物型”肌肉肌动蛋白基因簇的首次报道。这五个基因5'侧翼区域的共有序列是保守的，表明这些基因的表达受到协调控制。这对于在这种动物快速发育的胚胎中积累大量肌动蛋白可能是有利的。
