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Published September 1978 | public
Journal Article

Repetitive sequence transcripts in the mature sea urchin oocyte

Abstract

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 (>10^5 copies per oocyte), while others are rare (∼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 ∼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.

Additional Information

© 1978 MIT. Received April 13, 1978; revised June 8, 1978. This research was supported by a grant from the National Institute of Child Health and Human Development). F.D.C. and R.H.S. were supported by NIH training grants to the Division of Biology and the Division of Chemistry. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Additional details

Created:
August 19, 2023
Modified:
October 18, 2023