Abstract
Extrachromosomal circular DNA molecules are associated with genomic instability, and circles containing inverted repeats were suggested to be the early amplification products. Here we present for the first time the use of neutral-neutral two-dimensional (2D) gel electrophoresis as a technique for the identification, isolation, and characterization of heterogeneous populations of circular molecules. Using this technique, we demonstrated that in N-methyl-N'-nitro-N-nitrosoguanidine-treated simian virus 40-transformed Chinese hamster cells (CO60 cells), the viral sequences are amplified as circular molecules of various sizes. The supercoiled circular fraction was isolated and was shown to contain molecules with inverted repeats. 2D gel analysis of extrachromosomal DNA from CHO cells revealed circular molecules containing highly repetitive DNA which are similar in size to the simian virus 40-amplified molecules. Moreover, enhancement of the amount of circular DNA was observed upon N-methyl-N'-nitro-N-nitrosoguanidine treatment of CHO cells. The implications of these findings regarding the processes of gene amplification and genomic instability and the possible use of the 2D gel technique to study these phenomena are discussed.
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- Aladjem M. I., Lavi S. The mechanism of carcinogen-induced DNA amplification: in vivo and in vitro studies. Mutat Res. 1992 May;276(3):339–344. doi: 10.1016/0165-1110(92)90020-a. [DOI] [PubMed] [Google Scholar]
- Assum G., Böckle B., Fink T., Dmochewitz U., Krone W. Restriction analysis of chromosomal sequences homologous to single-copy fragments cloned from small polydisperse circular DNA (spcDNA). Hum Genet. 1989 Jun;82(3):249–254. doi: 10.1007/BF00291164. [DOI] [PubMed] [Google Scholar]
- Assum G., Fink T., Steinbeisser T., Fisel K. J. Analysis of human extrachromosomal DNA elements originating from different beta-satellite subfamilies. Hum Genet. 1993 Jun;91(5):489–495. doi: 10.1007/BF00217778. [DOI] [PubMed] [Google Scholar]
- Berko-Flint Y., Karby S., Hassin D., Lavi S. Carcinogen-induced DNA amplification in vitro: overreplication of the simian virus 40 origin region in extracts from carcinogen-treated CO60 cells. Mol Cell Biol. 1990 Jan;10(1):75–83. doi: 10.1128/mcb.10.1.75. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bertelsen A. H., Humayun M. Z., Karfopoulos S. G., Rush M. G. Molecular characterization of small polydisperse circular deoxyribonucleic acid from an African green monkey cell line. Biochemistry. 1982 Apr 27;21(9):2076–2085. doi: 10.1021/bi00538a015. [DOI] [PubMed] [Google Scholar]
- Beverley S. M., Coderre J. A., Santi D. V., Schimke R. T. Unstable DNA amplifications in methotrexate-resistant Leishmania consist of extrachromosomal circles which relocalize during stabilization. Cell. 1984 Sep;38(2):431–439. doi: 10.1016/0092-8674(84)90498-7. [DOI] [PubMed] [Google Scholar]
- Brewer B. J., Fangman W. L. The localization of replication origins on ARS plasmids in S. cerevisiae. Cell. 1987 Nov 6;51(3):463–471. doi: 10.1016/0092-8674(87)90642-8. [DOI] [PubMed] [Google Scholar]
- Brown P. C., Tlsty T. D., Schimke R. T. Enhancement of methotrexate resistance and dihydrofolate reductase gene amplification by treatment of mouse 3T6 cells with hydroxyurea. Mol Cell Biol. 1983 Jun;3(6):1097–1107. doi: 10.1128/mcb.3.6.1097. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Carroll S. M., DeRose M. L., Gaudray P., Moore C. M., Needham-Vandevanter D. R., Von Hoff D. D., Wahl G. M. Double minute chromosomes can be produced from precursors derived from a chromosomal deletion. Mol Cell Biol. 1988 Apr;8(4):1525–1533. doi: 10.1128/mcb.8.4.1525. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Carroll S. M., DeRose M. L., Kolman J. L., Nonet G. H., Kelly R. E., Wahl G. M. Localization of a bidirectional DNA replication origin in the native locus and in episomally amplified murine adenosine deaminase loci. Mol Cell Biol. 1993 May;13(5):2971–2981. doi: 10.1128/mcb.13.5.2971. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Carroll S. M., Gaudray P., De Rose M. L., Emery J. F., Meinkoth J. L., Nakkim E., Subler M., Von Hoff D. D., Wahl G. M. Characterization of an episome produced in hamster cells that amplify a transfected CAD gene at high frequency: functional evidence for a mammalian replication origin. Mol Cell Biol. 1987 May;7(5):1740–1750. doi: 10.1128/mcb.7.5.1740. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Carroll S. M., Trotter J., Wahl G. M. Replication timing control can be maintained in extrachromosomally amplified genes. Mol Cell Biol. 1991 Sep;11(9):4779–4785. doi: 10.1128/mcb.11.9.4779. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Cohen S., Hassin D., Karby S., Lavi S. Hairpin structures are the primary amplification products: a novel mechanism for generation of inverted repeats during gene amplification. Mol Cell Biol. 1994 Dec;14(12):7782–7791. doi: 10.1128/mcb.14.12.7782. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Dolf G., Meyn R. E., Curley D., Prather N., Story M. D., Boman B. M., Siciliano M. J., Hewitt R. R. Extrachromosomal amplification of the epidermal growth factor receptor gene in a human colon carcinoma cell line. Genes Chromosomes Cancer. 1991 Jan;3(1):48–54. doi: 10.1002/gcc.2870030109. [DOI] [PubMed] [Google Scholar]
- Eki T., Enomoto T., Murakami Y., Hanaoka F., Yamada M. Characterization of chromosome aberrations induced by incubation at a restrictive temperature in the mouse temperature-sensitive mutant tsFT20 strain containing heat-labile DNA polymerase alpha. Cancer Res. 1987 Oct 1;47(19):5162–5170. [PubMed] [Google Scholar]
- Fidler I. J., Hart I. R. The development of biological diversity and metastatic potential in malignant neoplasms. Oncodev Biol Med. 1982;4(1-2):161–176. [PubMed] [Google Scholar]
- Flores S. C., Sunnerhagen P., Moore T. K., Gaubatz J. W. Characterization of repetitive sequence families in mouse heart small polydisperse circular DNAs: age-related studies. Nucleic Acids Res. 1988 May 11;16(9):3889–3906. doi: 10.1093/nar/16.9.3889. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ford M., Davies B., Griffiths M., Wilson J., Fried M. Isolation of a gene enhancer within an amplified inverted duplication after "expression selection". Proc Natl Acad Sci U S A. 1985 May;82(10):3370–3374. doi: 10.1073/pnas.82.10.3370. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ford M., Fried M. Large inverted duplications are associated with gene amplification. Cell. 1986 May 9;45(3):425–430. doi: 10.1016/0092-8674(86)90328-4. [DOI] [PubMed] [Google Scholar]
- Fried M., Feo S., Heard E. The role of inverted duplication in the generation of gene amplification in mammalian cells. Biochim Biophys Acta. 1991 Oct 8;1090(2):143–155. doi: 10.1016/0167-4781(91)90095-4. [DOI] [PubMed] [Google Scholar]
- Fujimoto S., Tsuda T., Toda M., Yamagishi H. Transposon-like sequences in extrachromosomal circular DNA from mouse thymocytes. Proc Natl Acad Sci U S A. 1985 Apr;82(7):2072–2076. doi: 10.1073/pnas.82.7.2072. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gardner M. J., Feagin J. E., Moore D. J., Rangachari K., Williamson D. H., Wilson R. J. Sequence and organization of large subunit rRNA genes from the extrachromosomal 35 kb circular DNA of the malaria parasite Plasmodium falciparum. Nucleic Acids Res. 1993 Mar 11;21(5):1067–1071. doi: 10.1093/nar/21.5.1067. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gaubatz J. W. Extrachromosomal circular DNAs and genomic sequence plasticity in eukaryotic cells. Mutat Res. 1990 Sep-Nov;237(5-6):271–292. doi: 10.1016/0921-8734(90)90009-g. [DOI] [PubMed] [Google Scholar]
- Goz B., Carl P. L., Tlsty T. D. 1-beta-D-arabinofuranosylcytosine enhancement of resistance to several antineoplastic drugs in mammalian tissue culture cells. Mol Pharmacol. 1989 Sep;36(3):360–365. [PubMed] [Google Scholar]
- Grondin K., Papadopoulou B., Ouellette M. Homologous recombination between direct repeat sequences yields P-glycoprotein containing amplicons in arsenite resistant Leishmania. Nucleic Acids Res. 1993 Apr 25;21(8):1895–1901. doi: 10.1093/nar/21.8.1895. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hahn P. J., Nevaldine B., Longo J. A. Molecular structure and evolution of double-minute chromosomes in methotrexate-resistant cultured mouse cells. Mol Cell Biol. 1992 Jul;12(7):2911–2918. doi: 10.1128/mcb.12.7.2911. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hahn P., Kapp L. N., Morgan W. F., Painter R. B. Chromosomal changes without DNA overproduction in hydroxyurea-treated mammalian cells: implications for gene amplification. Cancer Res. 1986 Sep;46(9):4607–4612. [PubMed] [Google Scholar]
- Hanson S., Beverley S. M., Wagner W., Ullman B. Unstable amplification of two extrachromosomal elements in alpha-difluoromethylornithine-resistant Leishmania donovani. Mol Cell Biol. 1992 Dec;12(12):5499–5507. doi: 10.1128/mcb.12.12.5499. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Heartlein M. W., Latt S. A. Amplified inverted duplications within and adjacent to heterologous selectable DNA. Nucleic Acids Res. 1989 Feb 25;17(4):1697–1716. doi: 10.1093/nar/17.4.1697. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hightower R. C., Ruiz-Perez L. M., Wong M. L., Santi D. V. Extrachromosomal elements in the lower eukaryote Leishmania. J Biol Chem. 1988 Nov 15;263(32):16970–16976. [PubMed] [Google Scholar]
- Hirt B. Selective extraction of polyoma DNA from infected mouse cell cultures. J Mol Biol. 1967 Jun 14;26(2):365–369. doi: 10.1016/0022-2836(67)90307-5. [DOI] [PubMed] [Google Scholar]
- Hollis M., Hindley J. Human Sau3A repeated DNA is enriched in small polydisperse circular DNA from normal lymphocytes. Gene. 1986;46(2-3):153–160. doi: 10.1016/0378-1119(86)90399-9. [DOI] [PubMed] [Google Scholar]
- Huber M., Koller B., Gitler C., Mirelman D., Revel M., Rozenblatt S., Garfinkel L. Entamoeba histolytica ribosomal RNA genes are carried on palindromic circular DNA molecules. Mol Biochem Parasitol. 1989 Jan 15;32(2-3):285–296. doi: 10.1016/0166-6851(89)90077-7. [DOI] [PubMed] [Google Scholar]
- Hyrien O., Debatisse M., Buttin G., de Saint Vincent B. R. The multicopy appearance of a large inverted duplication and the sequence at the inversion joint suggest a new model for gene amplification. EMBO J. 1988 Feb;7(2):407–417. doi: 10.1002/j.1460-2075.1988.tb02828.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jones R. S., Potter S. S. Characterization of cloned human alphoid satellite with an unusual monomeric construction: evidence for enrichment in HeLa small polydisperse circular DNA. Nucleic Acids Res. 1985 Feb 11;13(3):1027–1042. doi: 10.1093/nar/13.3.1027. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kapler G. M., Coburn C. M., Beverley S. M. Stable transfection of the human parasite Leishmania major delineates a 30-kilobase region sufficient for extrachromosomal replication and expression. Mol Cell Biol. 1990 Mar;10(3):1084–1094. doi: 10.1128/mcb.10.3.1084. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kleinberger T., Etkin S., Lavi S. Carcinogen-mediated methotrexate resistance and dihydrofolate reductase amplification in Chinese hamster cells. Mol Cell Biol. 1986 Jun;6(6):1958–1964. doi: 10.1128/mcb.6.6.1958. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Krolewski J. J., Schindler C. W., Rush M. G. Structure of extrachromosomal circular DNAs containing both the Alu family of dispersed repetitive sequences and other regions of chromosomal DNA. J Mol Biol. 1984 Mar 25;174(1):41–54. doi: 10.1016/0022-2836(84)90364-4. [DOI] [PubMed] [Google Scholar]
- Krysan P. J., Calos M. P. Replication initiates at multiple locations on an autonomously replicating plasmid in human cells. Mol Cell Biol. 1991 Mar;11(3):1464–1472. doi: 10.1128/mcb.11.3.1464. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Krysan P. J., Haase S. B., Calos M. P. Isolation of human sequences that replicate autonomously in human cells. Mol Cell Biol. 1989 Mar;9(3):1026–1033. doi: 10.1128/mcb.9.3.1026. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kunisada T., Yamagishi H. Sequence organization of repetitive sequences enriched in small polydisperse circular DNAs from HeLa cells. J Mol Biol. 1987 Dec 20;198(4):557–565. doi: 10.1016/0022-2836(87)90199-9. [DOI] [PubMed] [Google Scholar]
- Kunisada T., Yamagishi H. Sequence repetition and genomic distribution of small polydisperse circular DNA purified from HeLa cells. Gene. 1984 Nov;31(1-3):213–223. doi: 10.1016/0378-1119(84)90212-9. [DOI] [PubMed] [Google Scholar]
- Lavi S. Carcinogen-mediated amplification of viral DNA sequences in simian virus 40-transformed Chinese hamster embryo cells. Proc Natl Acad Sci U S A. 1981 Oct;78(10):6144–6148. doi: 10.1073/pnas.78.10.6144. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lavi S., Etkin S. Carcinogen-mediated induction of SV40 DNA synthesis in SV40 transformed Chinese hamster embryo cells. Carcinogenesis. 1981;2(5):417–423. doi: 10.1093/carcin/2.5.417. [DOI] [PubMed] [Google Scholar]
- Lavi S., Winocour E. Acquisition of sequences homologous to host deoxyribonucleic acid by closed circular simian virus 40 deoxyribonucleic acid. J Virol. 1972 Feb;9(2):309–316. doi: 10.1128/jvi.9.2.309-316.1972. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Looney J. E., Hamlin J. L. Isolation of the amplified dihydrofolate reductase domain from methotrexate-resistant Chinese hamster ovary cells. Mol Cell Biol. 1987 Feb;7(2):569–577. doi: 10.1128/mcb.7.2.569. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ma C., Looney J. E., Leu T. H., Hamlin J. L. Organization and genesis of dihydrofolate reductase amplicons in the genome of a methotrexate-resistant Chinese hamster ovary cell line. Mol Cell Biol. 1988 Jun;8(6):2316–2327. doi: 10.1128/mcb.8.6.2316. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Martín-Parras L., Hernández P., Martínez-Robles M. L., Schvartzman J. B. Initiation of DNA replication in ColE1 plasmids containing multiple potential origins of replication. J Biol Chem. 1992 Nov 5;267(31):22496–22505. [PubMed] [Google Scholar]
- Misra R., Matera A. G., Schmid C. W., Rush M. G. Recombination mediates production of an extrachromosomal circular DNA containing a transposon-like human element, THE-1. Nucleic Acids Res. 1989 Oct 25;17(20):8327–8341. doi: 10.1093/nar/17.20.8327. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Misra R., Shih A., Rush M., Wong E., Schmid C. W. Cloned extrachromosomal circular DNA copies of the human transposable element THE-1 are related predominantly to a single type of family member. J Mol Biol. 1987 Jul 20;196(2):233–243. doi: 10.1016/0022-2836(87)90687-5. [DOI] [PubMed] [Google Scholar]
- Morgan W. F., Bodycote J., Fero M. L., Hahn P. J., Kapp L. N., Pantelias G. E., Painter R. B. A cytogenetic investigation of DNA rereplication after hydroxyurea treatment: implications for gene amplification. Chromosoma. 1986;93(3):191–196. doi: 10.1007/BF00292737. [DOI] [PubMed] [Google Scholar]
- Motejlek K., Assum G., Krone W., Kleinschmidt A. K. The size of small polydisperse circular DNA (spcDNA) in angiofibroma-derived cell cultures from patients with tuberous sclerosis (TSC) differs from that in fibroblasts. Hum Genet. 1991 May;87(1):6–10. doi: 10.1007/BF01213083. [DOI] [PubMed] [Google Scholar]
- Motejlek K., Schindler D., Assum G., Krone W. Increased amount and contour length distribution of small polydisperse circular DNA (spcDNA) in Fanconi anemia. Mutat Res. 1993 Mar;293(3):205–214. doi: 10.1016/0921-8777(93)90071-n. [DOI] [PubMed] [Google Scholar]
- Nalbantoglu J., Meuth M. DNA amplification--deletion in a spontaneous mutation of the hamster aprt locus: structure and sequence of the novel joint. Nucleic Acids Res. 1986 Nov 11;14(21):8361–8371. doi: 10.1093/nar/14.21.8361. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nonet G. H., Carroll S. M., DeRose M. L., Wahl G. M. Molecular dissection of an extrachromosomal amplicon reveals a circular structure consisting of an imperfect inverted duplication. Genomics. 1993 Mar;15(3):543–558. doi: 10.1006/geno.1993.1107. [DOI] [PubMed] [Google Scholar]
- Nowell P. C. The clonal evolution of tumor cell populations. Science. 1976 Oct 1;194(4260):23–28. doi: 10.1126/science.959840. [DOI] [PubMed] [Google Scholar]
- Oppenheim A. Separation of closed circular DNA from linear DNA by electrophoresis in two dimensions in agarose gels. Nucleic Acids Res. 1981 Dec 21;9(24):6805–6812. doi: 10.1093/nar/9.24.6805. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Papadopoulou B., Roy G., Ouellette M. Frequent amplification of a short chain dehydrogenase gene as part of circular and linear amplicons in methotrexate resistant Leishmania. Nucleic Acids Res. 1993 Sep 11;21(18):4305–4312. doi: 10.1093/nar/21.18.4305. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Passananti C., Davies B., Ford M., Fried M. Structure of an inverted duplication formed as a first step in a gene amplification event: implications for a model of gene amplification. EMBO J. 1987 Jun;6(6):1697–1703. doi: 10.1002/j.1460-2075.1987.tb02420.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Petrillo-Peixoto M. L., Beverley S. M. Amplified DNAs in laboratory stocks of Leishmania tarentolae: extrachromosomal circles structurally and functionally similar to the inverted-H-region amplification of methotrexate-resistant Leishmania major. Mol Cell Biol. 1988 Dec;8(12):5188–5199. doi: 10.1128/mcb.8.12.5188. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Riabowol K., Shmookler Reis R. J., Goldstein S. Interspersed repetitive and tandemly repetitive sequences are differentially represented in extrachromosomal covalently closed circular DNA of human diploid fibroblasts. Nucleic Acids Res. 1985 Aug 12;13(15):5563–5584. doi: 10.1093/nar/13.15.5563. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rice G. C., Ling V., Schimke R. T. Frequencies of independent and simultaneous selection of Chinese hamster cells for methotrexate and doxorubicin (adriamycin) resistance. Proc Natl Acad Sci U S A. 1987 Dec;84(24):9261–9264. doi: 10.1073/pnas.84.24.9261. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rio D. C. Molecular mechanisms regulating Drosophila P element transposition. Annu Rev Genet. 1990;24:543–578. doi: 10.1146/annurev.ge.24.120190.002551. [DOI] [PubMed] [Google Scholar]
- Ruiz J. C., Choi K. H., von Hoff D. D., Roninson I. B., Wahl G. M. Autonomously replicating episomes contain mdr1 genes in a multidrug-resistant human cell line. Mol Cell Biol. 1989 Jan;9(1):109–115. doi: 10.1128/mcb.9.1.109. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ruiz J. C., Wahl G. M. Chromosomal destabilization during gene amplification. Mol Cell Biol. 1990 Jun;10(6):3056–3066. doi: 10.1128/mcb.10.6.3056. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ruiz J. C., Wahl G. M. Formation of an inverted duplication can be an initial step in gene amplification. Mol Cell Biol. 1988 Oct;8(10):4302–4313. doi: 10.1128/mcb.8.10.4302. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rush M. G., Misra R. Extrachromosomal DNA in eucaryotes. Plasmid. 1985 Nov;14(3):177–191. doi: 10.1016/0147-619x(85)90001-0. [DOI] [PubMed] [Google Scholar]
- Schimke R. T. Gene amplification in cultured cells. J Biol Chem. 1988 May 5;263(13):5989–5992. [PubMed] [Google Scholar]
- Schimke R. T., Sherwood S. W., Hill A. B., Johnston R. N. Overreplication and recombination of DNA in higher eukaryotes: potential consequences and biological implications. Proc Natl Acad Sci U S A. 1986 Apr;83(7):2157–2161. doi: 10.1073/pnas.83.7.2157. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schindler C. W., Rush M. G. Discrete size classes of monkey extrachromosomal circular DNA containing the L1 family of long interspersed nucleotide sequences are produced by a general non-sequence specific mechanism. Nucleic Acids Res. 1985 Nov 25;13(22):8247–8258. doi: 10.1093/nar/13.22.8247. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schvartzman J. B., Adolph S., Martín-Parras L., Schildkraut C. L. Evidence that replication initiates at only some of the potential origins in each oligomeric form of bovine papillomavirus type 1 DNA. Mol Cell Biol. 1990 Jun;10(6):3078–3086. doi: 10.1128/mcb.10.6.3078. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stanfield S. W., Helinski D. R. Cloning and characterization of small circular DNA from Chinese hamster ovary cells. Mol Cell Biol. 1984 Jan;4(1):173–180. doi: 10.1128/mcb.4.1.173. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stanfield S., Helinski D. R. Small circular DNA in Drosophila melanogaster. Cell. 1976 Oct;9(2):333–345. doi: 10.1016/0092-8674(76)90123-9. [DOI] [PubMed] [Google Scholar]
- Sundin O., Varshavsky A. Terminal stages of SV40 DNA replication proceed via multiply intertwined catenated dimers. Cell. 1980 Aug;21(1):103–114. doi: 10.1016/0092-8674(80)90118-x. [DOI] [PubMed] [Google Scholar]
- Sunnerhagen P., Sjöberg R. M., Bjursell G. Increase of extrachromosomal circular DNA in mouse 3T6 cells on perturbation of DNA synthesis: implications for gene amplification. Somat Cell Mol Genet. 1989 Jan;15(1):61–70. doi: 10.1007/BF01534670. [DOI] [PubMed] [Google Scholar]
- Sunnerhagen P., Sjöberg R. M., Karlsson A. L., Lundh L., Bjursell G. Molecular cloning and characterization of small polydisperse circular DNA from mouse 3T6 cells. Nucleic Acids Res. 1986 Oct 24;14(20):7823–7838. doi: 10.1093/nar/14.20.7823. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tlsty T. D., Margolin B. H., Lum K. Differences in the rates of gene amplification in nontumorigenic and tumorigenic cell lines as measured by Luria-Delbrück fluctuation analysis. Proc Natl Acad Sci U S A. 1989 Dec;86(23):9441–9445. doi: 10.1073/pnas.86.23.9441. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tripp C. A., Wisdom W. A., Myler P. J., Stuart K. D. A multicopy, extrachromosomal DNA in Leishmania infantum contains two inverted repeats of the 27.5-kilobase LD1 sequence and encodes numerous transcripts. Mol Biochem Parasitol. 1992 Oct;55(1-2):39–50. doi: 10.1016/0166-6851(92)90125-4. [DOI] [PubMed] [Google Scholar]
- Von Hoff D. D., Forseth B., Clare C. N., Hansen K. L., VanDevanter D. Double minutes arise from circular extrachromosomal DNA intermediates which integrate into chromosomal sites in human HL-60 leukemia cells. J Clin Invest. 1990 Jun;85(6):1887–1895. doi: 10.1172/JCI114650. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Von Hoff D. D., Needham-VanDevanter D. R., Yucel J., Windle B. E., Wahl G. M. Amplified human MYC oncogenes localized to replicating submicroscopic circular DNA molecules. Proc Natl Acad Sci U S A. 1988 Jul;85(13):4804–4808. doi: 10.1073/pnas.85.13.4804. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wahl G. M. The importance of circular DNA in mammalian gene amplification. Cancer Res. 1989 Mar 15;49(6):1333–1340. [PubMed] [Google Scholar]
- White T. C., Fase-Fowler F., van Luenen H., Calafat J., Borst P. The H circles of Leishmania tarentolae are a unique amplifiable system of oligomeric DNAs associated with drug resistance. J Biol Chem. 1988 Nov 15;263(32):16977–16983. [PubMed] [Google Scholar]
- Windle B. E., Wahl G. M. Molecular dissection of mammalian gene amplification: new mechanistic insights revealed by analyses of very early events. Mutat Res. 1992 May;276(3):199–224. doi: 10.1016/0165-1110(92)90009-x. [DOI] [PubMed] [Google Scholar]
- Windle B., Draper B. W., Yin Y. X., O'Gorman S., Wahl G. M. A central role for chromosome breakage in gene amplification, deletion formation, and amplicon integration. Genes Dev. 1991 Feb;5(2):160–174. doi: 10.1101/gad.5.2.160. [DOI] [PubMed] [Google Scholar]
- Yamagishi H. Role of mammalian circular DNA in cellular differentiation. Bioessays. 1986 May;4(5):218–221. doi: 10.1002/bies.950040508. [DOI] [PubMed] [Google Scholar]
- Yamagishi H., Tsuda T., Fujimoto S., Toda M., Kato K., Maekawa Y., Umeno M., Anai M. Purification of small polydisperse circular DNA of eukaryotic cells by use of ATP-dependent deoxyribonuclease. Gene. 1983 Dec;26(2-3):317–321. doi: 10.1016/0378-1119(83)90205-6. [DOI] [PubMed] [Google Scholar]