SnapShot: DNA Polymerases I Prokaryotes

The nucleus and mitochondria of eukaryote cells and the nucleoid of prokaryote cells contain remarkable enzymes, called DNA polymerases, which ensure the faithful duplication of genetic material. These enzymatic machines incorporate the building blocks of DNA, deoxyribonucleotide triphosphates (dNTPs), into growing polynucleotide chains. The error rate of these enzymes is astonishingly low with only ~1 error for every 10 [superscript 9]–10[superscript 10] bases replicated. The first safeguard contributing to this low error rate is the ability of the DNA polymerase to discriminate among incoming dNTPs based on their complementarity to a parental DNA template. However, in the event of misincorporation, many DNA polymerases also have associated “proof-reading” activities that remove an inappropriately added dNTP, thus providing a second safeguard to protect the integrity of the genome. Moreover, cells use a variety of DNA polymerases, called translesion DNA polymerases, whose sole function is to enable recovery from specific genetic insults by endogenous and exogenous mutagens