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Eukaryotic DNA Polymerases
 

Eukaryotic DNA Polymerases - The cells of higher eukaryotes contain at least three DNA polymerases, alpha ,β, γ. Mitochondria from mammalian cells were considered to have a different DNA polymerase activity.

Recent work however, suggests that mitochondrial DNA polymerase may be a form of  γ -Polymerase. Alpha and γ polymerases have a molecular weight of over 100,000 while the molecular weight of β  polymerase is 30,000-50,000

Alpha polymerase has been referred to as the cytoplasmic DNA Polymerase, but it is probable that its in vivo location is in the nucleus. In animal cells the major part of alpha and β polymerase activity is located in the nucleus. β polymerase (which is located solely in the nucleus) can copy a poly(A) template but not alpha polymerase. β polymerase, however, cannot utilize poly(C) as a template.

DNA Polymerase Molecular Weight
α-Polymerase 120,000-300,000
β-Polymerase 30,000-50,000
γ-Polymerase 150,000-300,000



In general, β polymerase can utilize polydeoxyribose templates like poly(dA) or poly(dC) more efficiently than polyriboncleotide templates like poly(A) or poly(C).alpha polymerase. In addition to natural or synthetic DNA templates, γ-polymerase can copy a variety of polyribonucleotides like poly(A), poly(C) etc.

Mitochondrial (mt) DNA polymerase has a molecular weight similar to that of alpha polymerase. Its activity is also reported to be similar to that of alpha polymerase. If confirmed this would mean that there is no uniquely different class of mitochondrial DNA polymerases. Hence there would be three rather than four classes of cellular DNA polymerases.
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