Cell cycle checkpoints and it's regulations

STUDY ABOUT CELL CYCLE AND CHECKPOINTS AND IT'S REGULATIONS

1. CENTURION UNIVERSITY, BHUBANESWAR SCHOOL OF APPLIED SCIENCES M.Sc. In Zoology NAME – MUKTA MANJARI SAHOO REGD NO – 230705180023 SUBJECT- CELL AND MOLECULAR BIOLOGY TOPIC – CELL CYCLE AND IT’S REGULATIONS

2. CHECKPOINTS

3. G1 CHECKPOINT ( G1 restriction point) At the G1 checkpoint, a cell checks whether internal and external conditions are right for division. Here are some of the factors a cell might assess:
-Size: Is the cell large enough to divide?
-Nutrients: Does the cell have enough energy reserves or available nutrients to divide?
-Molecular signals: Is the cell receiving positive cues (such as growth factors) from neighbours?
-DNA integrity: Is any of the DNA damaged?

4. If a cell doesn’t get the go-ahead cues it needs at the
G1 checkpoint, it may leave the cell cycle and enter a resting state called G0 phase. Some cells-stay permanently in GO, while others resume dividing if conditions improve. G2 CHECKPOINT To make sure that cell division goes smoothly (produces healthy daughter cells with complete, undamaged DNA), the cell has an additional checkpoint before M phase, called the G2 checkpoint. At this stage, the cell will check:

5. -DNA integrity: Is any of the DNA damaged?
-DNA replication: Was the DNA completely copied during S phase?
If errors or damage are detected, the cell will pause at the G2 checkpoint to allow for repairs. If the checkpoint mechanisms detect problems with the DNA, the cell cycle is halted, and the cell attempts to either complete DNA replication or repair the damaged DNA.
If the damage is irreparable, the cell may undergo apoptosis, or programmed cell death. This self-destruction mechanism ensures that damaged DNA is not passed on to daughter cells and is important in preventing cancer.

6. M CHECKPOINT This occurs at metaphase. Anaphase-promoting complex (APC) regulates this checkpoint .This is also called spindle checkpoint.
This checks whether all chromosomes are properly attached to the spindle or not. This also governs the alignment of the chromosomes and integrity of the spindles. If there are mistakes then it delays the cell in entering into anaphase from metap hase.

7. CELL CYCLE REGULATORS The cell cycle is regulated by cycles. 1.Cyclins 2. Cyclin-dependent kinases (CDKs)
3. Cyclin-dependent kinase inhibitors (CDKIs) 1. CYCLIN : Their concentration varies during the cell cycle. Cyclins are the family of proteins which regulates the cell cycle . There are several types of cyclins that are active in different parts of the cell cycle and causes phosphorylation of CDK.
There are four basic types found in humans and most other eukaryotes:G1cyclins, G1/S cyclins, S cyclins, and M cyclins.

8. The levels of the different cyclins vary considerably across the cell cycle, as shown in the diagram at right. A typical cyclin is present at low levels for most of the cycle, but increases strongly at the stage where it’s needed. M cyclin, for example, peaks dramatically at the transition from G2 to M phase. G1 cyclins are unusual in that they are needed for much of the cell cycle.

9. 2.CYCLIN-DEPENDENT KINSASES (CDKS) These are a family of protein kinases that regulates the cell cycle. They are present in all known eukaryotic cells.
In order to drive the cell cycle forward, a cyclin must activate or inactivate many target proteins inside of the cell. Cyclins drive the events of the cell cycle by partnering with a family of enzymes called the cyclin-dependent kinases (Cdks). A lone Cdk is inactive, but the binding of a cyclin activates it, making it a functional enzyme and allowing it to modify target proteins.

10. 3. CYCLIN-DEPENDENT KINASE INHIBITORS(CDKIS) CDKI is a protein which inhibits cyclin-dependent kinase (CDK). Cell cycle progression is negatively controlled by cyclin-dependent kinases-inhibitors (called CDIs, CKIs or CDKIs). These are involved in cell cycle arrest at the G1 phase.

11. Are those which control the changes necessary for cell division. They include:- Cyclins & Cyclin-dependent kinases( Cdks ) They include ;- Rb proteins & P53 gene - Inhibitors of Cdks which are of 2 types
Ink family (Inhibitors of kinases) –P19,P15
CIP family ( cdks inhibitory proteins) – P21, P57

12. REFERENCES 1.Allen, .(2019). Freshwater Fishes of Australia. T.F.H Publications: New Jersey, USA.222(14):pp.124-129