Pauletti, Giovanni and Lai, Eric and Attardi, Giuseppe (1990) Early appearance and long-term persistence of the submicroscopic extrachromosomal elements (amplisomes) containing the amplified DHFR genes in human cell lines. Proceedings of the National Academy of Sciences of the United States of America, 87 (8). pp. 2955-2959. ISSN 0027-8424 http://resolver.caltech.edu/CaltechAUTHORS:PAUpnas90
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Submicroscopic extrachromosomal elements (amplisomes) containing amplified dihydrofolate reductase (DHFR) genes have been investigated in a methotrexate-resistant derivative of the human cell line HeLa BU25, 10B3, by field-inversion gel electrophoresis. The amount and kinetics of formation of these elements have been correlated with the level and time course of overall DHFR gene amplification. The amplisomes account for the great majority and possibly the totality of the amplified DHFR genes in 10B3 cells. They appear very early during the development of methotrexate resistance and increase in parallel with the amplified genes. These observations suggest that these elements are involved in an early event, possibly the first event, of gene amplification in this system. Amplisomes tend to be lost from 10B3 cells in the absence of selective pressure, although much more slowly than expected from simple dilution of nonreplicating elements. Surprisingly, under selective pressure, these elements have shown no tendency to become integrated into chromosomes or to generate minute chromosomes over a period of almost 1 year, in contrast to what has been described in other systems.
|Additional Information:||Copyright © 1990 by the National Academy of Sciences. Contributed by Giuseppe Attardi, January 16, 1990. This work was supported by a grant from the Margaret E. Early Medical Research Trust, by a National Institutes of Health grant (GM11726) to G.A., and by a Fellowship (AIFCR 88-104) of the American-Italian Foundation for Cancer Research to G.P. We are grateful to the personnel of Jet Propulsion Laboratory for their help in the γ-irradiation experiments, to Dr. Ray White for the DNA probe, to Drs. Barry Maurer and Norman Davidson for valuable advice and discussion, and to Drs. Michael King and Anne Chomyn for critically reading the manuscript. The technical assistance of Ms. Benneta Keeley and Ms. Lisa Tefo is gratefully acknowledged. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.|
|Subject Keywords:||cytogenetic abnormalities; drug resistance; pulsed-field gel electrophoresis|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||07 Feb 2006|
|Last Modified:||26 Dec 2012 08:45|
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