This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Carroll, S M Articles by Wahl, G M Search for Related Content PubMed PubMed Citation Articles by Carroll, S M Articles by 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.

ABSTRACT

In a previous study (G. M. Wahl, B. Robert de Saint Vincent, and M. L. De Rose, Nature (London) 307:516-520, 1984), we used gene transfer of a CAD cosmid to demonstrate that gene position profoundly affects amplification frequency. One transformant, T5, amplified the donated CAD genes at a frequency at least 100-fold higher than did the other transformants analyzed. The CAD genes in T5 and two drug-resistant derivatives were chromosomally located. In this report, we show that a subclone of T5 gives rise to an extrachromosomal molecule (CAD episome) containing the donated CAD genes. Gel electrophoresis indicated that the CAD episome is approximately 250 to 300 kilobase pairs, and a variety of methods showed that it is a covalently closed circle. We show that the CAD episome replicates semiconservatively and approximately once per cell cycle. Since the CAD cosmid, which comprises most of the CAD episome, does not replicate autonomously when transfected into cells, our results indicate that either the process which generated the episome resulted in a cellular origin of DNA replication being linked to the CAD sequences or specific rearrangements within the episome generated a functional origin. The implications of these results for mechanisms of gene amplification and the genesis of minute chromosomes are discussed.

This article has been cited by other articles:

• Wang, L., Lin, C.-M., Brooks, S., Cimbora, D., Groudine, M., Aladjem, M. I. (2004). The Human {beta}-Globin Replication Initiation Region Consists of Two Modular Independent Replicators. Mol. Cell. Biol. 24: 3373-3386 [Abstract] [Full Text]  
• Tano, K., Dunn, W. C., Darroudi, F., Shiota, S., Preston, R. J., Natarajan, A. T., Mitra, S. (1997). Amplification of the DNA Repair Gene O6-Methylguanine-DNA Methyltransferase Associated with Resistance to Alkylating Drugs in a Mammalian Cell Line. J. Biol. Chem. 272: 13250-13254 [Abstract] [Full Text]  
• Wang, M, Shouse, S, Lipes, B, Kim, U J, Shizuya, H, Lai, E (1996). Bacterial artificial chromosome cloning and mapping of a 630-kb human extrachromosomal structure.. Genome Res. 6: 612-619 [Abstract]  
• Kusaba, H, Kohno, K, Asakuno, K, Kuwano, M, Okumura, K, Green, E D, Schlessinger, D, Wada, M (1995). Functional expression of yeast artificial chromosome-human multidrug resistance genes in mouse cells.. Genome Res. 5: 245-258 [Abstract]  
• Trask, B J, Hamlin, J L (1989). Early dihydrofolate reductase gene amplification events in CHO cells usually occur on the same chromosome arm as the original locus.. Genes Dev. 3: 1913-1925 [Abstract]