Abstract
DNA polymerase mu (pol mu), which is related to terminal deoxynucleotidyl transferase and DNA polymerase beta, is thought to be involved in non-homologous end joining and V(D)J recombination. Pol mu is induced by ionizing radiation and exhibits low fidelity. Analysis of translesion replication by purified human pol mu revealed that it bypasses a synthetic abasic site with high efficiency, using primarily a misalignment mechanism. It can also replicate across two tandem abasic sites, using the same mechanism. Pol mu extends primers whose 3'-terminal nucleotides are located opposite the abasic site. Most remarkably, this extension occurs via a mode of nucleotidyl transferase activity, which does not depend on the sequence of the template. This is not due to simple terminal nucleotidyl transferase activity, because pol mu is unable to add dNTPs to an oligo(dT)29 primer or to a blunt end duplex oligonucleotide under standard conditions. Thus, pol mu is a dual mode DNA-synthesizing enzyme, which can act as either a classical DNA polymerase or as a non-canonical, template-dependent, but sequence-independent nucleotidyl transferase. To our knowledge, this is the first report on a DNA-synthesizing enzyme with such properties. These activities may be required for its function in non-homologous end joining in the processing of DNA ends prior to ligation.
Highlights
DNA polymerase 1 is a recently identified member of the X family of DNA polymerases
Unlike terminal deoxynucleotidyltransferase, which is specific to the immune system, pol is expressed in additional tissues [1, 2]
When extending a primer terminus located opposite an abasic site, pol adds each of the four dNTPs, regardless of the sequence of the template
Summary
DNA polymerase (pol ) is a recently identified member of the X family of DNA polymerases. It has an outstanding tendency to form frameshift mutations, directed by its ability to misalign the primer terminus with short downstream homologies (microhomology search) [6] Based on this property, it was proposed that pol functions in NHEJ by searching homology between two broken ends, followed by filling in small gaps. When extending a primer terminus located opposite an abasic site, pol adds each of the four dNTPs, regardless of the sequence of the template. To our knowledge, this is the first report on a template-dependent but non-instructed nucleotidyl transferase activity
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have