Junghans, R. P. and Hu, S. and Knight, C. A. and Davidson, N. (1977) Heteroduplex Analysis of Avian RNA Tumor Viruses. Proceedings of the National Academy of Sciences of the United States of America, 74 (2). pp. 477-481. ISSN 0027-8424. http://resolver.caltech.edu/CaltechAUTHORS:JUNpnas77
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Electron microscopic heteroduplex analysis of avian RNA tumor viruses has been undertaken by using 35S viral RNA and long, complementary DNA synthesized in vitro. In this initial study, heteroduplex molecules were formed between complementary DNA from Rous sarcoma virus [Prague B strain (Pr-B)] and RNAs from Pr-B and Rous sarcoma virus [Prague C strain (Pr-C)] and from their transformation defective (td) derivatives, td-Pr-B and td-Pr-C. In the case of heteroduplexes with the td viruses, a deletion loop was observed of the order of two kilobases in size and less than one kilobase from the 3' terminus of the RNA. This deletion probably spans part or all of the sequences of one or more genes in the nondefective sarcoma virus which are essential for cell transformation. The sizes and the positions of the deletions in the td-Pr-B and td-Pr-C viruses were slightly, but significantly, different. No nonhomology features were observed in the Pr-B· Pr-C hybrids, thus confirming the close genetic relatedness of the two viruses. All heteroduplexes contained a proportion of circular and dimer molecules. This observation is a direct demonstration that (-) strand DNA transcription begins at an internal position of the RNA genome, proceeds to the 5' end, reinitiates at the 3' end of the RNA, and copies the remainder of the viral genome. Other implications for models of RNA tumor virus replication are also developed from these data.
|Additional Information:||Copyright © 1977 by the National Academy of Sciences Contributed by Norman Davidson, November 8, 1976 We wish to acknowledge the expert technical assistance of Valerie Ng and Yu-Sun Liu. We thank Peter Duesberg for his interest and valuable discussions as well as for supplying cells and viruses. We wish to thank Welcome Bender for critical reading of the manuscript prior to publication and William Haseltine and Harold Varmus for sharing unpublished data with us. The major portion of the electron microscopy was performed by one of the authors (S.H.). R.J. is a post-doctoral fellow of the Helen Hay Whitney Society. This work was supported by Grant no. AI 00634 from the National Institute of Allergy and Infectious Diseases (to C.A.K.) and by Contract NO-1-CP-43306 with the Virus Cancer Program of the National Cancer Institute (to N.D.).|
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