In vertebrate smooth muscle, phosphorylation of the myosin regulatory light chain activates contraction in Ca2+ dependent manner.

TLS Online TPP Program

#Id: 8640

#Section 3: Genetics, Cellular and Molecular Biology

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

#Section 3: Genetics, Cellular and Molecular Biology

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

#Section 3: Genetics, Cellular and Molecular Biology

TLS Online TPP Program

#Id: 8643

#Section 3: Genetics, Cellular and Molecular Biology

When E2Fs are bound to Rb, not only are they transcriptionally inactive, but they also function to repress transcription by recruiting chromatin-modifying enzymes that promote deacetylation and methylation of specific histone lysines.

TLS Online TPP Program

#Id: 8644

#Section 3: Genetics, Cellular and Molecular Biology

Phosphorylation on multiple sites by G1 CDKs blocks Rb from associating with E2F and promotes its export out of the nucleus.

TLS Online TPP Program

#Id: 8645

#Section 3: Genetics, Cellular and Molecular Biology

Rb protein regulation by G1 CDKs in mammalian cells is analogous to Whi5 regulation by Cln3-CDK in yeast.