Yamaguchi M, Ohba Y
Department of Biology, Faculty of Science, Kanazawa University, Japan.
Zoolog Sci. 1997 Dec;14(6):947-52. doi: 10.2108/zsj.14.947.
We isolated two cDNAs, termed D7 and C2 in the present study, from a cDNA library of the 16-cell embryo of the sea urchin Anthocidaris crassispina. The nucleotide sequence was determined completely for D7, and partially for C2. D7 does not have any significant open reading frames. Both D7 and C2 contain a common sequence that is 62% homologous to the sea urchin retroposon family 1 (SURF1). The SURF1 is a short interspersed repetitive element identified from the sea urchin Strongylocentrotus purpuratus, and is reported to be transcribed by RNA polymerase III. The structural feature of D7 and C2, however, suggests that they may be transcribed by RNA polymerase II. RT-PCR analyses revealed that (1) both D7 and C2 transcripts exist as a maternal RNA in the egg, (2) they appear evenly distributed in the 16-cell embryo, and (3) C2 transcripts are present throughout the development up to the gastrula, while D7 transcripts decrease in amount after the early cleavage stage.
在本研究中，我们从厚刺海胆16细胞期胚胎的cDNA文库中分离出两个cDNA，分别命名为D7和C2。我们完整测定了D7的核苷酸序列，部分测定了C2的核苷酸序列。D7没有任何明显的开放阅读框。D7和C2都包含一个与海胆反转录转座子家族1（SURF1）有62%同源性的共同序列。SURF1是从紫球海胆中鉴定出的一种短散在重复元件，据报道由RNA聚合酶III转录。然而，D7和C2的结构特征表明它们可能由RNA聚合酶II转录。逆转录聚合酶链反应（RT-PCR）分析显示：（1）D7和C2转录本在卵中均作为母源RNA存在；（2）它们在16细胞期胚胎中分布均匀；（3）C2转录本在整个发育过程直至原肠胚期都存在，而D7转录本在早期卵裂阶段后数量减少。
