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A novel nuclease activity from Xenopus laevis releases short oligomers from 5′‐ends of double‐and single‐stranded DNA
Author(s) -
Reichenberger Susanne,
Brüll Nicole,
Feldmann Elke,
Göttlich Bernd,
Vielmetter Walter,
Pfeiffer Petra
Publication year - 1996
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1046/j.1365-2443.1996.d01-245.x
Subject(s) - xenopus , exonuclease , biology , dna , double stranded , nuclease , oligonucleotide , double strand , context (archaeology) , homologous recombination , microbiology and biotechnology , exonuclease iii , dna damage , biophysics , genetics , dna polymerase , gene , escherichia coli , paleontology
Background : Double‐strand breaks in chromosomal DNA of eucaryotic cells are assumed to be repaired by mechanisms of illegitimate recombination capable of direct rejoining of the broken ends. Cell‐free extracts of Xenopus laevis eggs efficiently perform these end joining reactions with any pair of noncomplementary DNA termini whose single‐stranded 5′‐ or 3′‐overhangs do not exceed a length of ≈ 10 nt. Results : Using hairpin‐shaped oligonucleotides that allow the construction of double‐strand break termini with 5′‐ or 3′‐overhangs of defined length and sequence we show that 5′‐overhangs of more than 9–10 nt are exonucleolytically resected in the extract to produce shorter 5′‐overhangs that can be metabolized in the end joining reaction. 5′‐recessed ends in double‐stranded DNA with 3′‐overhangs of more than 2 nt as well as the 5′‐ends of single‐stranded DNA also serve as substrates for the exonuclease activity. In all cases, oligomers of about 10 nt are released from the 5′‐ends. Conclusions : We describe here a novel 5′‐exonuclease activity present in eggs from Xenopus laevis that reproducibly removes decameric oligonucleotides from 5′‐ends of double‐ and single‐stranded DNA. A possible function of this unusual activity is discussed in the context of homologous and illegitimate genetic recombination processes.