Costantini F D, Scheller R H, Britten R J, Davidson E H
Cell. 1978 Sep;15(1):173-87. doi: 10.1016/0092-8674(78)90093-4.
The expression of interspersed repetitive sequences in the RNA of mature sea urchin oocytes was investigated. 3H-DNA tracers representing short interspersed repetitive sequences a few hundred nucleotides long, and long repetitive sequences approximately 2000 nucleotides long, were prepared from genomic DNA of the sea urchin, Strongylocentrotus purpuratus. These tracers were reacted with excess RNA from the mature oocyte. About 80% of the reactable short repeat tracer and 35% of the long repeat tracer hybridized. Thus most of the repetitive sequence families in the short repeat tracer are represented in oocyte RNA, and transcripts complementary to both strands of many repeat sequences are present. The kinetics of the reaction show that some transcripts are highly prevalent (greater than 10(5) copies per oocyte), while others are rare (approximately 10(3) copies per oocyte). Nine cloned repetitive sequences were labeled, strand-separated and reacted with the oocyte RNA. Transcripts of both strands of all nine repeats were found in the RNA. The prevalence of transcripts of the cloned repeat families varied from approximately 3000 to 100,000 copies per oocyte. Studies with both cloned and genomic tracers show that transcript prevalence is independent of the genomic reiteration frequency of the transcribed repetitive sequences. Most of the families represented by prevalent transcripts have fewer than 200 copies per haploid genome. The RNA molecules with which the cloned repeats react are at least 1000-2000 nucleotides in length. Other experiments show that a majority of the members of repeat families represented by prevalent transcripts in the oocyte RNA are interspersed among single-copy sequence elements in the genome.
对成熟海胆卵母细胞RNA中散布重复序列的表达进行了研究。从紫海胆（Strongylocentrotus purpuratus）的基因组DNA制备了代表几百个核苷酸长的短散布重复序列和大约2000个核苷酸长的长重复序列的3H-DNA示踪剂。这些示踪剂与成熟卵母细胞中过量的RNA反应。约80%的可反应短重复示踪剂和35%的长重复示踪剂发生了杂交。因此，短重复示踪剂中的大多数重复序列家族都存在于卵母细胞RNA中，并且存在与许多重复序列的两条链互补的转录本。反应动力学表明，一些转录本高度普遍（每个卵母细胞大于10^5个拷贝），而另一些则很少见（每个卵母细胞约10^3个拷贝）。对9个克隆的重复序列进行标记、链分离并与卵母细胞RNA反应。在RNA中发现了所有9个重复序列两条链的转录本。克隆重复序列家族转录本的普遍程度在每个卵母细胞约3000至100,000个拷贝之间变化。对克隆示踪剂和基因组示踪剂的研究表明，转录本的普遍程度与转录重复序列的基因组重复频率无关。由普遍转录本代表的大多数家族每个单倍体基因组的拷贝数少于200个。与克隆重复序列反应的RNA分子长度至少为1000 - 2000个核苷酸。其他实验表明，卵母细胞RNA中由普遍转录本代表的重复序列家族的大多数成员散布在基因组中的单拷贝序列元件之间。
