DNA polymerase II is a type of DNA polymerase: a category of enzymes that synthesize identical copies of existing DNA, allowing dividing cells to pass this genetic information on to their daughter cells. DNA polymerase II is found only in prokaryotes, or unicellular organisms, such as archaea, and simple bacteria that lack membrane-bound nuclei and organelles.
Prokaryotes have five known types of DNA polymerases, numbered I to V. DNA polymerases replicate DNA by synthesizing sequences of nucleotides, the molecular components of DNA. There are only four types of nucleotides in DNA. The specific order of these nucleotides is the genetic code that controls the creation, maintenance and operation of all living cells. DNA polymerases read the order of these nucleotides and copy them exactly to create new strands of DNA.
DNA polymerase II was discovered in E. coli bacteria by Thomas Kornberg in 1970. DNA polymerase II supports the activity of DNA polymerase III, which is the principal DNA-replicating enzyme in prokaryotes. If damaged DNA stalls the progress of DNA polymerase III, DNA polymerase II plays a part in reinitiating synthesis at a different point in the DNA strand, allowing DNA polymerase III to continue replication beyond the damaged area.
DNA polymerase II also checks newly synthesized strands of DNA for accuracy. If there are any errors in replication, DNA polymerase II removes and discards the segment of inaccurate DNA.