DNA translocation blockage, a general mechanism of cleavage site selection by type I restriction enzymes

Janscak, Pavel ; MacWilliams, Maria P. ; Sandmeier, Ursula ; Nagaraja, Valakunja ; Bickle, Thomas A. (1999) DNA translocation blockage, a general mechanism of cleavage site selection by type I restriction enzymes EMBO Journal, 18 (9). pp. 2638-2647. ISSN 0261-4189

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Official URL: http://www.nature.com/emboj/journal/v18/n9/abs/759...

Related URL: http://dx.doi.org/10.1093/emboj/18.9.2638


Type I restriction enzymes bind to a specific DNA sequence and subsequently translocate DNA past the complex to reach a non-specific cleavage site. We have examined several potential blocks to DNA translocation, such as positive supercoiling or a Holliday junction, for their ability to trigger DNA cleavage by type I restriction enzymes. Introduction of positive supercoiling into plasmid DNA did not have a significant effect on the rate of DNA cleavage by EcoAI endonuclease nor on the enzyme's ability to select cleavage sites randomly throughout the DNA molecule. Thus, positive supercoiling does not prevent DNA translocation. EcoR124II endonuclease cleaved DNA at Holliday junctions present on both linear and negatively supercoiled substrates. The latter substrate was cleaved by a single enzyme molecule at two sites, one on either side of the junction, consistent with a bidirectional translocation model. Linear DNA molecules with two recognition sites for endonucleases from different type I families were cut between the sites when both enzymes were added simultaneously but not when a single enzyme was added. We propose that type I restriction enzymes can track along a DNA substrate irrespective of its topology and cleave DNA at any barrier that is able to halt the translocation process.

Item Type:Article
Source:Copyright of this article belongs to Nature Publishing Group.
Keywords:DNA Supercoiling; DNA Translocation; Holliday Junction; Type I Restriction Enzyme
ID Code:26934
Deposited On:08 Dec 2010 12:58
Last Modified:17 May 2016 10:13

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