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Resolution of synthetic Holliday junctions in DNA by an endonuclease activity from calf thymus.
Author(s) -
Elborough K. M.,
West S. C.
Publication year - 1990
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1990.tb07484.x
Subject(s) - nuclease , endonuclease , cleavage (geology) , holliday junction , biology , restriction enzyme , dna , nucleotide , microbiology and biotechnology , genetics , gene , paleontology , dna repair , fracture (geology)
Extracts of calf thymus have been fractionated to reveal a nuclease activity that specifically cleaves model Holliday junctions in vitro. The products of cleavage are unbranched linear duplex DNA molecules. Using synthetic four‐way junctions, we show that the major sites of cutting are diametrically opposed, at sites one nucleotide from the base of the junction. Other types of four‐way junctions, including pseudo‐cruciform structures and cruciforms extruded from supercoiled plasmids, are also cleaved by the nuclease. The Mr of the partially purified activity, determined by gel filtration, is approximately 75,000. The calf thymus enzyme provides the first example of an endonuclease from a higher eukaryote that acts specifically on branch points in DNA, and indicates that junction‐resolving proteins are normal constituents of somatic cells.