Open AccessProof‐reading 3′→5′ exonucleases isolated from rat liver nuclei
Author(s) -
BELYAKOVA Natalya V.,
KLEINER Natalya E.,
KRAVETSKAYA Tatyana P.,
LEGINA Olga K.,
NARYZHNY Stanislav N.,
PERRINO Fred W.,
SHEVELEV Igor V.,
KRUTYAKOV Valery M.
Publication year - 1993
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1993.tb18269.x
Subject(s) - dna polymerase , proofreading , exonuclease , biology , polymerase , microbiology and biotechnology , dna replication , dna , dna clamp , dna synthesis , biochemistry , dna polymerase ii , polymerase chain reaction , reverse transcriptase , gene
Mammalian nuclear DNA polymerases α and β are known to be devoid of the editing 3′→5′ exonucleolytic activity. Presumably this activity could be effected by the exonucleases non‐associated covalently with DNA polymerases. Two 3′→5′ exonucleases of 40 kDa and 50 kDa (exo‐40 and exo‐50) have been isolated from rat liver nuclei and purified to near homogeneity. They are shown to excise mismatched nucleotides from poly[d(A‐T)] template, respectively, 10‐fold and 2‐fold faster than the matched ones. Upon addition of either of these exonucleases to the DNA polymerase α from rat liver or calf thymus, the fidelity of in‐vitro reproduction of the primed DNA from bacteriophage φX174 amber 3 is increased 5–10‐fold, levels of exonuclease and DNA‐polymerase activities being similar. Extrapolation of in‐vitro DNA‐replication fidelity to the cellular levels of activities of the exonucleases and the α‐polymerase suggests that exonucleolytic proofreading augments the accuracy of DNA synthesis by 2–3 orders of magnitude.