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Synthesis and turnover of polysomal mRNAs in sea urchin embryos

Galau, Glenn A. and Lipson, Edward D. and Britten, Roy J. and Davidson, Eric H. (1977) Synthesis and turnover of polysomal mRNAs in sea urchin embryos. Cell, 10 (3). pp. 415-432. ISSN 0092-8674. doi:10.1016/0092-8674(77)90029-0.

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The synthesis and turnover kinetics of polysomal mRNA have been measured in sea urchin embryos. Polysomes were isolated from stages ranging between mesenchyme blastula and late gastrula Strongylocentrotus purpuratus embryos which had been exposed to exogenous ^3H-guanosine. The amount of radioactivity incorporated into messenger and ribosomal RNAs was determined separately as a function of time, and the precursor pool specific activity was measured in the same embryos. Synthesis and decay rate constants were extracted from the data by a leastsquares procedure. Per embryo, the rate of mRNA synthesis was calculated to be about 0.13 pg min_(−1), while the rate of rRNA synthesis is about 0.022 pg min^(−1). The newly synthesized mRNA turns over with a half-time of 5.7 hr. The data support only a single decay rate for the mRNA, but small fractions of mRNA decaying at different rates cannot be excluded. Previous studies have shown that a minor fraction of the mRNA includes the least abundant, most highly diverse set of messages (“complex class” mRNAs). To determine whether mRNAs of the complex class are synthesized and degraded at similar rates, labeled mRNA was measured in hybrids formed in mRNA excess reactions with single copy DNA. These experiments showed that complex class mRNAs represent an approximately proportional amount of the new mRNA synthesis, and turn over at the same average rate as does the bulk of the mRNA. Most of the mRNAs in the embryo polysomes are newly synthesized, rather than maternal. This statement refers both to complex class mRNAs and to prevalent mRNAs. Considering the sequence homology between embryo and oocyte mRNAs shown earlier, these results indicate that many of the same structural genes active during oogenesis are being transcribed in embryos at these stages.

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Additional Information:© 1977 by MIT. Received October 12, 1976; revised November 22, 1976. The authors are pleased to acknowledge the helpful and critical review of this manuscript by Professor Norman Davidson of this Institute. This work was supported by grants from the NIH and by a grant from the NSF. G. A.G. was supported by USPHS training grant and by The National Foundation March of Dimes Grant.
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U.S. Public Health Service (USPHS)UNSPECIFIED
National Foundation - March of DimesUNSPECIFIED
Issue or Number:3
Record Number:CaltechAUTHORS:20160812-124415301
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Official Citation:Glenn A. Galau, Edward D. Lipson, Roy J. Britten, Eric H. Davidson, Synthesis and turnover of polysomal mRNAs in sea urchin embryos, Cell, Volume 10, Issue 3, March 1977, Pages 415-432, ISSN 0092-8674, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69598
Deposited By: Ruth Sustaita
Deposited On:12 Aug 2016 22:34
Last Modified:11 Nov 2021 04:16

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