POLM
Encyclopedia
DNA polymerase mu is a human protein encoded by the POLM gene
.
. It participates in resynthesis of damaged or missing nucleotides during the non-homologous end joining (NHEJ)
pathway of DNA repair
. Pol μ interacts with Ku
and DNA ligase IV
, which also participate in NHEJ. It is structurally and functionally related to pol λ, and, like pol λ, pol μ has a BRCT domain
that is thought to mediate interactions with other DNA repair proteins. Unlike pol λ, however, pol μ has the unique ability to add a base to a blunt end that is templated by the overhang on the opposite end of the double-strand break. Pol μ is also closely related to terminal deoxynucleotidyl transferase (TdT)
, a specialized DNA polymerase that adds random nucleotides to DNA ends during V(D)J recombination
, the process by which B-cell
and T-cell receptor diversity is generated in the vertebrate
immune system
. Like TdT, pol μ participates in V(D)J recombination, but only during heavy chain rearrangements. This is distinct from pol λ, which is involved in light chain rearrangements.
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
.
Function
Pol μ is a member of the X family of DNA polymerasesDNA polymerase
A DNA polymerase is an enzyme that helps catalyze in the polymerization of deoxyribonucleotides into a DNA strand. DNA polymerases are best known for their feedback role in DNA replication, in which the polymerase "reads" an intact DNA strand as a template and uses it to synthesize the new strand....
. It participates in resynthesis of damaged or missing nucleotides during the non-homologous end joining (NHEJ)
Non-homologous end joining
Non-homologous end joining is a pathway that repairs double-strand breaks in DNA. NHEJ is referred to as "non-homologous" because the break ends are directly ligated without the need for a homologous template, in contrast to homologous recombination, which requires a homologous sequence to guide...
pathway of DNA repair
DNA repair
DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and radiation can cause DNA damage, resulting in as many as 1...
. Pol μ interacts with Ku
Ku (protein)
Ku is a protein that binds to DNA double-strand break ends and is required for the non-homologous end joining pathway of DNA repair. Ku is evolutionarily conserved from bacteria to human. The ancestral bacterial Ku is a homodimer...
and DNA ligase IV
LIG4
LIG4 is a human gene that encodes the protein DNA Ligase IV.-Further reading:...
, which also participate in NHEJ. It is structurally and functionally related to pol λ, and, like pol λ, pol μ has a BRCT domain
BRCT domain
BRCA1 C Terminus domain is a family of evolutionarily related proteins.The BRCT domain is found predominantly in proteins involved in cell cycle checkpoint functions responsive to DNA damage, for example as found in the breast cancer DNA-repair protein BRCA1...
that is thought to mediate interactions with other DNA repair proteins. Unlike pol λ, however, pol μ has the unique ability to add a base to a blunt end that is templated by the overhang on the opposite end of the double-strand break. Pol μ is also closely related to terminal deoxynucleotidyl transferase (TdT)
Terminal Deoxynucleotidyl Transferase
Terminal deoxynucleotidyl transferase , also known as DNA nucleotidylexotransferase or terminal transferase, is a specialized DNA polymerase expressed in immature, pre-B, pre-T lymphoid cells, and acute lymphoblastic leukemia/lymphoma cells...
, a specialized DNA polymerase that adds random nucleotides to DNA ends during V(D)J recombination
V(D)J recombination
VJ recombination, also known as somatic recombination, is a mechanism of genetic recombination in the early stages of immunoglobulin and T cell receptors production of the immune system...
, the process by which B-cell
B-cell receptor
The B-cell receptor is a transmembrane receptor protein located on the outer surface of B-cells. The receptor's binding moiety is composed of a membrane-bound antibody that, like all antibodies, has a unique and randomly-determined antigen-binding site...
and T-cell receptor diversity is generated in the vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
. Like TdT, pol μ participates in V(D)J recombination, but only during heavy chain rearrangements. This is distinct from pol λ, which is involved in light chain rearrangements.