Binding of the repressor to the operator sequence blocks binding of RNA polymerase and so inhibits transcription.

TLS Online TPP Program

#Id: 8637

#Unit 2. Cellular Organization

The G1 cyclin-CDK complex (Cln3-CDK in yeast) stimulates the formation of G1/S phase cyclin-CDKs, which initiate bud formation, centrosome duplication, and DNA replication.

TLS Online TPP Program

#Id: 8638

#Unit 2. Cellular Organization

Once sufficient Cln3 is synthesized from its mRNA, Cln3-CDK complexes phosphorylate and inactivate the transcriptional repressor Whi5.

TLS Online TPP Program

#Id: 8639

#Unit 2. Cellular Organization

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: 8640

#Unit 2. Cellular Organization

In vertebrates, Rb is the major guardian of the cell cycle, integrating information about DNA damage and cell growth

TLS Online TPP Program

#Id: 8641

#Unit 2. Cellular Organization

Rb binds the activation domains of a E2F transcription factors, in the cytoplasm to prevent them from turning on the genes required for cell cycle progression.

TLS Online TPP Program

#Id: 8642

#Unit 2. Cellular Organization