In the treated cell, samples have shown a reduction of cell number in G1 phase compared to that of control. and a corresponding hike in apoptotic cell number was observed.
Dear Ayisha!
The reasons for the decrease in cells in the G1 phase and an increase in apoptotic cells can be the effect of physical factors (radiation, UV, radiation therapy), chemical factors (chemotherapy, drugs, toxins, antibiotics), bacteria and viruses, the effect of hormones, growth factors, cytokines, chemokines , immunological reactions (antibodies, complement, exposure to cytotoxic T-lymphocytes). All these factors affect the cell membrane or its DNA, since in the G1 phase (presynthetic phase), protein synthesis is observed, preparation of DNA for replication in the S phase, the effect of any of these factors reduces the number of cells in the G1 phase and increases the number of apoptotic cells.
Please You look at following review article:
Article Control of cell cycle transcription during G1 and S phases
G1 phase, which is also known as either growth or gap phase is an intermediate phase between the end of cell division in mitosis and the beginning of DNA replication during S phase. During this phase, the cells take time to synthesize various proteins and grows in preparation for DNA replication and cell division in late stages of cell cycle. Interestingly, during this time the cells has to undergo a quality control check which helps in making the decision whether or not to progress towards S phase. If a cell does not clear or qualify to pass through restricted check-points to enter S phase, it enters the dormant G0 phase in which growth or division ceases and those cells are destined to undergo death by apoptosis. So, it’s not a surprise when you see a little low cell number in G1 phase of the cell cycle. Moreover, as your are seeing this in cells treated with some external agents, that may further complement for reduced cell number due to possible associated toxicity
Hello Ayisha
If the substance that you are using for treating the cells is DNA damaging then the defective cells are arrested in the G1 phase and not allowed to enter the S phase. This arrest enables the DNA repair machinery to repair the DNA damage and prevent apoptosis. However, if the damage is severe then the cell switches over to apoptosis. p53 protein which is called the GUARDIAN OF THE GENOME is a major player in this process, and it transcribes apoptotic proteins that bring about apoptosis of cells which are beyond repair.
Thank you.
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