Changes in DNA polymerase alpha, beta, gamma activities during early development of the teleost fish Misgurnus...

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 activities of DNA polymerases alpha and beta. A high activity of DNA polymerase alpha was revealed in the egg extract (2.0 X 10(3) 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 two 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 degrees 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 threefold by the completion of epiboly (20 h).