DNA-POLYMERASE-ALPHA IN EARLY DEVELOPMENT OF THE TELEOST FISH MISGURNUS-FOSSILIS L (LOACH)

In mature oocytes and embryos of the teleost fish Misgurnus fossilis L . (loach) DNA-polymerase ct is found in two forms, alpha(1) and alpha( 2), alpha(1) being a truncated form of alpha(2). We studied the subuni t composition of DNA-polymerase alpha, a change in which may be respon sible for the conversion of alpha(2) into alpha(1) during embryogenesi s. Two-dimensional electrophoresis of the proteins present in DNA-poly merase alpha(1) and alpha(2) preparations revealed in each of them fou r major polypeptides with apparent molecular masses of 168, 67, 60, an d 56 kD; these probably correspond to the four subunits known for euca ryotic DNA-polymerase alpha-primase complex. The pI values of these po lypeptides in alpha(1) and alpha(2) preparations ranged from 5.55 to 5 .70 and from 5.45 to 5.60, respectively. Both preparations possess low primase-activity, detectable only in the presence of no less than 0.7 unit of DNA-polymerase activity in the reaction mixture. Ribonucleoti de-dependent DNA synthesis is carried out both on native and on synthe tic templates in the mode of positive cooperation. The data indicate t hat the DNA-polymerase alpha-primase complex found in leach oocytes ha s enzymatic activity which is considerably different from those of oth er similar eucaryotic complexes. Thus, the observed changes in DNA-pol ymerase a during early development of the teleost fish Misgurnus fossi lis L. do not affect its subunit composition and are probably due to a conformational rearrangement in the DNA-polymerase alpha-primase comp lex.