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A Measurement of the Sequence Complexity of Polysomal Messenger RNA in Sea Urchin Embryos

Galau, Glenn A. and Britten, Roy J. and Davidson, Eric H. (1974) A Measurement of the Sequence Complexity of Polysomal Messenger RNA in Sea Urchin Embryos. Cell, 2 (1). pp. 9-21. ISSN 0092-8674. doi:10.1016/0092-8674(74)90003-8.

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The first measurement has been made of the number of diverse mRNA sequences (mRNA sequence complexity) in the total polysomes of a eucaryotic system, the sea urchin gastrula. mRNA was purified of nuclear RNA and any other heterogeneous RNA contaminants by release from polysomes with puromycin. Trace quantities of labeled nonrepetitive DNA fragments were hybridized with an excess of mRNA. The hybridization reaction followed ideal first order kinetics in mRNA concentration. At completion of the hybridization reaction, 1.35% of the nonrepetitive DNA was present as mRNA-DNA hybrid. The hybridized DNA was extracted and was at least 70% hybridizable with mRNA, demonstrating a 50-fold purification of the expressed sequences. This purified DNA fraction reassociated with excess unfractionated sea urchin DNA at a rate identical to that of the total nonrepetitive DNA tracer. The mRNA had therefore been hybridized to nonrepetitive DNA sequence, and the amount of hybrid could be used as a direct measure of the mRNA sequence complexity. The complexity of the gastrula mRNA can be calculated as about 17 million nucleotides, sufficient to comprise some 14,000 distinct structural genes. This result also provides an estimate of the number of diverse proteins being translated in the gastrula. From the rate of mRNA-DNA hybrid formation, we estimate that about 8% of the mRNA belongs to this complex class, and that less than 500 copies of each species of message in this class exist per embryo. Most of the mRNA population consists of a relatively small number of diverse species represented a much larger number of times.

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Additional Information:© 1974 by MIT. Received February 15; Revised 25 February 1974. We are extremely grateful to our colleagues Dr. Barbara Hough, Dr. William Klein, and Dr. Michael J. Smith for critical discussion and many other forms of assistance. This work was supported by grants from the U.S. Public Health Service and the National Science Foundation. G. A. G. is a predoctoral fellow on a U. S. Public Health Service grant.
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U.S. Public Health Service (USPHS)UNSPECIFIED
NIH Predoctoral FellowshipUNSPECIFIED
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Official Citation:Glenn A. Galau, Roy J. Britten, Eric H. Davidson, A measurement of the sequence complexity of polysomal messenger RNA in sea urchin embryos, Cell, Volume 2, Issue 1, May 1974, Pages 9-21, ISSN 0092-8674, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69557
Deposited By: Ruth Sustaita
Deposited On:11 Aug 2016 17:15
Last Modified:11 Nov 2021 04:16

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