Maize DNA polymerase alpha is phosphorylated by a PCNA-associated cyclin/Cdk complex: effect of benzyladenine.
The activity of maize DNA polymerases 1 and 2 (delta and alpha-type enzymes, respectively) is stimulated during germination if embryo axes are imbibed in the presence of benzyladenine. In vivo, DNA pol 2 is a phosphorotein that appears to be maximally phosphorylated previous to the S phase start time (by 12 h of germination, Coello and Vázquez-Ramos 1995a). We find that, in vitro, a PCNA-associated cyclin/kinase activity isolated from maize axes acquires an increasing capacity to phosphorylate DNA pol 2 as germination advances; moreover, the PCNA-associated kinase isolated from BA-treated maize axes germinated at 3 h phosphorylates DNA pol 2 at the same level observed in samples of axes germinated for 13 h in the absence of exogenous BA. PCNA-associated kinase activity from BA-treated axes germinated at 13 h maximal using DNA pol 2 as substrate. However, there is no modification in DNA polymerase activity as a consequence of protein phosphorylation. Results are discussed in terms of their significance for cell cycle regulation during seed germination.
Gómez Roig
Edurne
E
Departamento de Bioquímica, Facultad de Química, UNAM, Avenida Universidad y Copilco, México 04510, D.F. jorman@servidor.unam.mx
Vázquez-Ramos
Jorge M
JM
D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001593:Benzyl Compounds; D002453:Cell Cycle / Q000187:drug effects; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D003583:Cytokinins / Q000494:pharmacology; D004256:DNA Polymerase I / Q000378:metabolism*; D018525:Germination; D007701:Kinetin; D010766:Phosphorylation; D010940:Plant Proteins / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011687:Purines; D003313:Zea mays / Q000166:cytology / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
D001593:Benzyl Compounds; D016213:Cyclins; D003583:Cytokinins; D010940:Plant Proteins; D018809:Proliferating Cell Nuclear Antigen; D011687:Purines; D018844:Cyclin-Dependent Kinases; D004256:DNA Polymerase I; D000225:Adenine; C480551:benzylaminopurine; D007701:Kinetin