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The E1 Protein of Bovine Papilloma Virus 1 is an ATP-Dependent DNA Helicase

Liu Yang, Ian Mohr, Erik Fouts, Daniel A. Lim, Michael Nohaile and Michael Botchan
Proceedings of the National Academy of Sciences of the United States of America
Vol. 90, No. 11 (Jun. 1, 1993), pp. 5086-5090
Stable URL: http://www.jstor.org/stable/2362227
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The E1 Protein of Bovine Papilloma Virus 1 is an ATP-Dependent DNA Helicase
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Abstract

For efficient DNA replication of papillomaviruses, only two viral-encoded proteins, E1 and E2, are required. Other proteins and factors are provided by the host cell. E2 is an enhancer of both transcription and replication and is known to help E1 bind cooperatively to the origin of DNA replication. E1 is sufficient for replication in extracts prepared from permissive cells, but the activity is enhanced by E2. Here we show that purified E1 can act as an ATP-dependent DNA helicase. To measure this activity, we have used strand displacement, unwinding of topologically constrained DNA, denaturation of duplex fragments, and electron microscopy. The ability of E1 to unwind circular DNA is found to be independent of origin-specific viral DNA sequences under a variety of experimental conditions. In unfractionated cellular extracts, E1-dependent viral DNA replication is origin-dependent, but at elevated E1 concentrations, replication can occur on nonorigin-containing DNA templates. This conversion from an origin-dependent replication system to a nonspecific initiator system is discussed in the context of the current understanding of the initiation of chromosomal DNA replication.

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