G1 Phase: Cell Cycle Regulation Checkpoints

G1 PHASE

Evaluating Growth Signals

Determining Nutrient Availability

DNA Integrity

-Signals are sent to encourage or discourage cells from entering cell cycle

-These growth signals cause CDK to add phosphate group to RB protein

-E2F is released from RB when phosphorylated to bind with DNA

-If growth signals are sufficient , a cell pass through the G1

-A cell ensures that nutrient levels are adequate before committing cell division

-Starving cell enters G0 and phosphate groups are removed from RB

-When nutrients become available , CDKs bring about phosphorylation to RB and releases E2F

-E2F binds with DNA and produce proteins to complete the cell cycle

-DNA must be free from damage and errors to undergo cell division

-p53 is involved in the regulation of repairing DNA

-CDK phosphorylates p53 and binds with DNA and repair proteins are produced

-If the DNA is repaired it will allowed to complete G1 , but if not , cell cycle will be halted or apoptosis will occur