Hello All
to continue with cell cycle
When cyclins are complexed with CDKs they become activated.
The cyclinD CDK 4&6 has a target protein called Rb protein.
Rb is a tumor suppressor protein. It is found to be mutated in cancer patients.
In normal cell Rb protein remains under phosphorylated especialy during G0 and G1 phase.
Its activity can be changed by level of phosphorylation.
It has affinity towards E2F which is a transcription factor in under phosphorylated state.
So binding of Rb to E2F suppress the activity of E2F.
The cyclinD CDK 4&6 complex phosphorylate Rb and its affinity towards E2F decreases and E2F after separating from E2F becomes activated and since it is a transcription factor, after activation it helps expression of genes required in cell cycle progression.
Another target of CDK4&6 and cyclin D complex is Cyclin E.
Cyclin E binds with CDK 2 and target the MCM helicase.
MCM helicases after activation unwinds the DNA for replication.
The DNA is scanned by ATM and ATR protein for any DNA damage. They are kinases.
ATM is activated if it find double strand damage and ATR activates by single strand damage.
ATM and ATR phosphorylate p53 protein and phosphorylation of p53 stabilizes it. after stabilization the level of p53 increases and they expresses cip and kip family of protein as p53 is transcription factor for them, which are discussed in earlier blog. Cip and Kip activation leads to cell cycle arrest in G1 phase.
CDK1 and cyclin B target is condensin protein which are required for chromosome activation in the S phase.
Lamins are also phosphoryated by CDK1 and cyclin B and they get depolymerised after phosphorylaton.
Microtubule associated protein are also the targets of this complex and get depolymerised.
Rest I will discuss in next blog.
to continue with cell cycle
When cyclins are complexed with CDKs they become activated.
The cyclinD CDK 4&6 has a target protein called Rb protein.
Rb is a tumor suppressor protein. It is found to be mutated in cancer patients.
In normal cell Rb protein remains under phosphorylated especialy during G0 and G1 phase.
Its activity can be changed by level of phosphorylation.
It has affinity towards E2F which is a transcription factor in under phosphorylated state.
So binding of Rb to E2F suppress the activity of E2F.
The cyclinD CDK 4&6 complex phosphorylate Rb and its affinity towards E2F decreases and E2F after separating from E2F becomes activated and since it is a transcription factor, after activation it helps expression of genes required in cell cycle progression.
Another target of CDK4&6 and cyclin D complex is Cyclin E.
Cyclin E binds with CDK 2 and target the MCM helicase.
MCM helicases after activation unwinds the DNA for replication.
The DNA is scanned by ATM and ATR protein for any DNA damage. They are kinases.
ATM is activated if it find double strand damage and ATR activates by single strand damage.
ATM and ATR phosphorylate p53 protein and phosphorylation of p53 stabilizes it. after stabilization the level of p53 increases and they expresses cip and kip family of protein as p53 is transcription factor for them, which are discussed in earlier blog. Cip and Kip activation leads to cell cycle arrest in G1 phase.
CDK1 and cyclin B target is condensin protein which are required for chromosome activation in the S phase.
Lamins are also phosphoryated by CDK1 and cyclin B and they get depolymerised after phosphorylaton.
Microtubule associated protein are also the targets of this complex and get depolymerised.
Rest I will discuss in next blog.
Thanks Sakshi....Your blogs are very good and informative.
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