The Holliday junction resolvase SpCCE1 prevents mitochondrial DNA aggregation in Schizosaccharomyces pombe |
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Authors: | Doe C L Osman F Dixon J Whitby M C |
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Institution: | (1) Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK E-mail: whitby@bioch.ox.ac.uk Tel.: +44 1865 275192; fax: +44 1865 275297, GB |
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Abstract: | SpCCE1 (YDC2) from Schizosaccharomyces pombe is a DNA structure-specific endonuclease that resolves Holliday junctions in vitro. To investigate the in vivo function of
SpCCE1 we made an Spcce1::ura4
+
insertion mutant strain. This strain is viable and, despite being devoid of the Holliday junction resolvase activity that
is readily detected in fractionated extracts from wild-type cells, exhibits normal levels of UV sensitivity and spontaneous
or UV-induced mitotic recombination. In accordance with the absence of a nuclear phenotype, we show by fluorescence microscopy
that a SpCCE1-GFP fusion localises exclusively to the mitochondria of S. pombe. In Saccharomyces cerevisiae the homologue of SpCCE1, CCE1, is known to function in the mitochondria where its role appears to be to remove recombination junctions and thus
facilitate mitochondrial DNA segregation. A similar function can probably be attributed to SpCCE1 in S. pombe, since the majority of mitochondrial DNA from the Spcce1::ura4
+
strain is in an aggregated form apparently due to extensive interlinking of DNA molecules by recombination junctions. Surprisingly,
this marked effect on the conformation of mitochondrial DNA results in little or no effect on proliferation or viability of
the Spcce1::ura4
+
strain. Possible explanations are discussed.
Received: 28 October 1999 / Accepted: 28 March 2000 |
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Keywords: | DNA repair Endonuclease Holliday junction Mitochondria Recombination |
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