ARTICLE

SELECTIVE INHIBITION OF GENETIC TRANSCRIPTION IN SEA URCHIN EMBRYOS : Incorporation of 5-Bromodeoxyuridine into Low Molecular Weight Nuclear DNA

Brian L. Kotzin ¹ and Robert F. Baker ¹

¹ From the Department of Biological Sciences, University of Southern California, Los Angeles, California 90007

Experimental evidence suggests that exposure of sea urchin gastrulae to 5-bromodeoxyuridine (BUdR), an analog of thymidine, causes a reduction in the rate of synthesis of some RNA species usually transcribed at this stage of development. In pulse-chase experiments, ³H (in gastrula stage 8–15S nuclear DNA labeled with BUdR-³H) could not be chased, with unlabeled BUdR, into 20–60S size-range DNA; in similar experiments in which gastrulae were pulsed with thymidine-³H and then chased with unlabeled thymidine, ³H in 8–15S nuclear DNA could be extensively chased into 20–60S DNA. DNA-RNA hybridization assays indicate that gastrula stage nuclear DNA in the range of 20–60S has greater sequence homology for gastrula stage RNA-³H than does nuclear DNA of similar size-range taken from gastrulae exposed to BUdR for 1 hr. An explanation is offered for the effect of BUdR on transcription and DNA replication in sea urchin embryos.

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This article has been cited by other articles:

• Wortzman, M., Baker, R. (1981). Two classes of single-stranded regions in DNA from sea urchin embryos. Science 211: 588-590 [Abstract]  
• Dickinson, D., Baker, R. (1979). 5-Bromodeoxyuridine inhibits sequence changes within inverted repeat DNA during embryogenesis. Science 205: 816-818 [Abstract]  

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