DNA polymerase alpha also known as ''Pol α'' is an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

complex found in

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

s that is involved in initiation of

DNA replication In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all life, living organisms, acting as the most essential part of heredity, biolog ...

. The DNA polymerase alpha complex consists of 4 subunits:

POLA1 DNA polymerase alpha catalytic subunit is an enzyme that in humans is encoded by the ''POLA1'' gene. Function This gene encodes the p180 catalytic subunit of DNA polymerase α-primase. Pol α has limited processivity and lacks 3′ exonucle ...

POLA2 DNA polymerase alpha subunit 2 is an enzyme that in humans is encoded by the ''POLA2'' gene. Interactions POLA2 has been shown to interact with PARP1. See also * DNA Polymerase A DNA polymerase is a member of a family of enzymes that catalyz ...

PRIM1 DNA primase small subunit is an enzyme that in humans is encoded by the ''PRIM1'' gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that ...

, and

PRIM2 DNA primase large subunit is an enzyme that in humans is encoded by the ''PRIM2'' gene. The replication of DNA in eukaryotic cells is carried out by a complex chromosomal replication apparatus, in which DNA polymerase alpha and primase are two ...

. Pol α has limited

processivity In molecular biology and biochemistry, processivity is an enzyme's ability to catalyze "consecutive reactions without releasing its substrate". For example, processivity is the average number of nucleotides added by a polymerase enzyme, such as ...

and lacks 3′

exonuclease Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end (exo) of a polynucleotide chain. A hydrolyzing reaction that breaks phosphodiester bonds at either the 3′ or the 5′ end occurs. Its close relative is th ...

activity for proofreading errors. Thus it is not well suited to efficiently and accurately copy long templates (unlike Pol

Delta Delta commonly refers to: * Delta (letter) (Δ or δ), the fourth letter of the Greek alphabet * D (NATO phonetic alphabet: "Delta"), the fourth letter in the Latin alphabet * River delta, at a river mouth * Delta Air Lines, a major US carrier ...

and

Epsilon Epsilon (, ; uppercase , lowercase or ; ) is the fifth letter of the Greek alphabet, corresponding phonetically to a mid front unrounded vowel or . In the system of Greek numerals it also has the value five. It was derived from the Phoenic ...

). Instead, it plays a more limited role in replication. Pol α is responsible for the initiation of DNA replication at origins of replication (on both the leading and lagging strands) and during synthesis of

Okazaki fragment Okazaki fragments are short sequences of DNA nucleotides (approximately 150 to 200 base pairs long in eukaryotes) which are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA ...

s on the lagging strand. The Pol α complex (pol α-DNA primase complex) consists of four subunits: the catalytic subunit POLA1, the regulatory subunit

, and the small and the large primase subunits PRIM1 and PRIM2 respectively. Once primase has created the RNA primer, Pol α starts replication elongating the primer with ~20 nucleotides.

Structure

DNA polymerase alpha, like DNA primase, contains iron-sulfur clusters, that are critical in

electron transport An electron transport chain (ETC) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this ...

that uses DNA itself to transfer electrons at very high speeds; this process is involved in detecting DNA damage, and may also be involved in a feedback between the primase complex and the DNA polymerase alpha.

References

External links

* EC 2.7.7 DNA replication DNA-binding proteins {{2.7-enzyme-stub