Oct 15, 1989

Modulation of the DNA scanning activity of the Micrococcus luteus UV endonuclease

The Journal of Biological Chemistry
R W Hamilton, R S Lloyd

Abstract

Micrococcus luteus UV endonuclease incises DNA at the sites of ultraviolet (UV) light-induced pyrimidine dimers. The mechanism of incision has been previously shown to be a glycosylic bond cleavage at the 5'-pyrimidine of the dimer followed by an apyrimidine endonuclease activity which cleaves the phosphodiester backbone between the pyrimidines. The process by which M. luteus UV endonuclease locates pyrimidine dimers within a population of UV-irradiated plasmids was shown to occur, in vitro, by a processive or "sliding" mechanism on non-target DNA as opposed to a distributive or "random hit" mechanism. Form I plasmid DNA containing 25 dimers per molecule was incubated with M. luteus UV endonuclease in time course reactions. The three topological forms of plasmid DNA generated were analyzed by agarose gel electrophoresis. When the enzyme encounters a pyrimidine dimer, it is significantly more likely to make only the glycosylase cleavage as opposed to making both the glycosylic and phosphodiester bond cleavages. Thus, plasmids are accumulated with many alkaline-labile sites relative to single-stranded breaks. In addition, reactions were performed at both pH 8.0 and pH 6.0, in the absence of NaCl, as well as 25,100, and 250 mM NaC...Continue Reading

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Mentioned in this Paper

Gephyromantis luteus
Micrococcus luteus
Methoxyamine hydrochloride
Electrophoresis, Agar Gel
Buglossidium luteum
Endonuclease Activity
DNA-(apurinic or apyrimidinic site) lyase
Micrococcus Luteus UV Endonuclease Activity
Cytokinesis of the Fertilized Ovum
Mimulus luteus

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