A SINGLE P34(CDC2) PROTEIN-KINASE (ENCODED BY NIMX(CDC2)) IS REQUIREDAT G(1) AND G(2) IN ASPERGILLUS-NIDULANS

We have cloned and sequenced a homolog of cdc2 from Aspergillus nidula ns that can complement the Schizosaccharomyces pombe cdc2-33 mutation. The gene was deleted and is required for continued nuclear DNA replic ation but not for mitochondrial DNA replication. Three different tempe rature-sensitive alleles were generated by reverse genetics. All of th e mutations generate the nim phenotype of A. nidulans. The new gene wa s designated nimX(cdc2) as it is not allelic to any of the other nim g enes (nimA to nimW) of A. nidulans. Reciprocal shift experiments place an essential function for nimX(cdc2) in G(1) and G(2). Antipeptide an tibodies were generated that detect NIMX(cdc2), and antisera were also generated to detect NIME(cyclinB). Th, two p34(cdc2) protein species previously detected in A. nidulans, p34 and p37, both precipitate usin g NIMX(cdc2) C-terminus-specific antibodies but only p34 co-precipitat es with NIME(cyclinB) Dephosphorylation of denatured p34 converts it t o the p37 form, showing p37 to be the non-phosphorylated form of NIMX( cdc2). The phosphorylation of p34 is therefore associated With its int eraction with NIME(cyclinB).