Protein kinase that acts both on serines and on tyrosines. It acts as a dosage-dependent negative regulator of entry into mitosis (G2 to M transition). Phosphorylates and inhibits cdc2. ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Binds 2 magnesium ions per subunit. Negatively regulated by phosphorylation in the M-phase. Phosphorylated in the C-terminal by NIM1/CDR1. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. WEE1 subfamily.