title: A site-specific single-strand endonuclease from the eukaryote Chlamydomonas.
abstract: We have found a unique deoxyribonuclease in extracts of the eukaryotic green alga Chlamydomonas. When incubated with viral DNA from adenovirus-2, this enzyme produces discrete fragments that form bands upon electrophoresis in an agarose gel. Site specificity of the enzymatic cleavage examined by identifying the 5'-terminal nucleotides in cleaved adenovirus-2 DNA and by studies with synthetic polynucleotides of defined sequence, indicates that the initial endonucleolytic cleavage occurs at a site containing a deoxythymidine residue. Electron microscopy of cleaved adenovirus-2 DNA revealed single-strand segments within duplex DNA. We propose that the enzyme acts by making initial site-specific single-strand incisions, followed by subsequent excision on the same strand, producing a gapped duplex molecule; and that double-strand scissions result from limited occurrence of overlapping single-strand gaps on complementary strands.
mesh_terms: D001483:Base Sequence; D002696:Chlamydomonas / Q000201:enzymology*; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004279:DNA, Viral / Q000378:metabolism; D003851:Deoxyribonucleases / Q000378:metabolism; D004720:Endonucleases / Q000302:isolation & purification / Q000378:metabolism*; D008970:Molecular Weight; D013936:Thymidine / Q000378:metabolism
chemical_list: D004277:DNA, Single-Stranded; D004279:DNA, Viral; D003851:Deoxyribonucleases; D004720:Endonucleases; D013936:Thymidine
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