This article is about the DNA Polymerase. For the RNA Polymerase, see RNA polymerase II

RNA polymerase II

RNA polymerase II is an enzyme found in eukaryotic cells. It catalyzes the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA. A 550 kDa complex of 12 subunits, RNAP II is the most studied type of RNA polymerase...

DNA polymerase II (also known as DNA Pol II or Pol II) is a prokaryotic

Prokaryote

The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

 DNA polymerase

DNA 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....

 most likely involved in 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...

.

The enzyme is 90 kDa

KDA

KDA may refer to:* Karachi Development Authority* Kongsberg Defence & Aerospace* Kotelawala Defence Academy* Kramer Design Associates* Lithium diisopropylamide, KDA is the potassium analogue of lithium diisopropylamideOr kDa may refer to:...

 in size and is coded by the polB gene

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...

. DNA Pol II can synthesize DNA new base pairs at an average rate of between 40 and 50 nucleotides/second. Strains lacking the gene show no defect in growth or replication. Synthesis of Pol II is induced during the stationary phase of cell growth. This is a phase in which little growth and DNA synthesis

DNA synthesis

DNA synthesis commonly refers to:*DNA replication - DNA biosynthesis *Polymerase chain reaction - enzymatic DNA synthesis *Oligonucleotide synthesis - chemical synthesis of nucleic acids...

 occurs. It is also a phase in which the DNA can accumulate damage

Mutation

In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

 such as short gaps, which act as a block to DNA Pol III. Under these circumstances, Pol II helps to overcome the problem because it can reinitiate DNA synthesis downstream of gaps. Pol II has a low error rate but it is much too slow to be of any use in normal DNA synthesis.
Pol II differs from Pol I in that it lacks a 5'->3' exonuclease activity, and cannot use a nicked duplex template.