Phosphorylation of Whi5 promotes its export out of the nucleus, allowing the transcription factor complex SBF to induce transcription of the G1/S phase cyclin genes CLN1 and CLN2.

TLS Online TPP Program

#Id: 8865

#Section 3: Genetics, Cellular and Molecular Biology

The phosphorylation state of T14 and Y15 is controlled by a dual-specificity protein kinase known as Wee1 and a pair of dual-specificity phosphatases, Cdc25B and Cdc25C (Threonine 14 is not phosphorylated in S. pombe CDK1)

TLS Online TPP Program

#Id: 8866

#Section 3: Genetics, Cellular and Molecular Biology

TLS Online TPP Program

#Id: 8867

#Section 3: Genetics, Cellular and Molecular Biology

Cdc25B is act as a starter phosphatase that initiates CDK1 activation

Cdc25C is the workhorse phosphatase that activates the vast majority of cyclin-CDK1 complexes

TLS Online TPP Program

#Id: 8868

#Section 3: Genetics, Cellular and Molecular Biology

TLS Online TPP Program

#Id: 8869

#Section 3: Genetics, Cellular and Molecular Biology

Yeast cells with a defective wee1+ gene activate mitotic CDKs prematurely and premature entry into mitosis (smaller than normal cells

TLS Online TPP Program

#Id: 8870

#Section 3: Genetics, Cellular and Molecular Biology

Fission yeast cells carrying a CDK1 mutation in which the tyrosine-15 residue is replaced by phenylalanine

show the same premature mitotic CDK activation and entry into mitosis.