Changes in DNA polymerase alpha, beta, gamma activities during early development of the teleost fish Misgurnus fossilis (loach)

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Abstract
DNA polymerase .alpha., .beta., .gamma. activities were determined after fractionation of loach (Misgurnus, fossilis) cell extracts in glycerol gradients. The extracts of mature eggs, liver and testes cells yielded similar specific activities of DNA polymerase .gamma. (9-15 units/g protein) but differed markedly in the specific activites of DNA polymerases .alpha. and .beta.. A high activity of DNA polymerase .alpha. was revealed in the egg extract (2.0 .times. 103 units/g protein), while no DNA polymerase .alpha. activity was detected in liver cells. The specific .beta.-polymerase activity in the extract of mature eggs was extremely low (3.6 units/g protein), about 2 orders of magnitude lower than the enzyme activity in the extracts of liver or testes cells. The specific activity of DNA polymerases .alpha. and .gamma. changes insignificantly during oocyte maturation and embryogenesis up to the stage of hatching (50 h at 21.5.degree. C). As the mass of oocytes and embryos remains virtually unchanged at the stages studied, no substantial changes were observed in the .alpha. and .gamma.-polymerase activities per egg or embryo. The specific .beta.-polymerase activity in embryo cells increases about 3-fold by the completion of epiboly (20 h).