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#G1 checkpoint

2 public questions tagged with this topic.

Cell Cycle Regulation

What is the role of p53 in the G1 checkpoint?

G1 progression toward S phase is driven by cyclin-dependent kinases CDK4/6-cyclin D and CDK2-cyclin E that phosphorylate retinoblastoma protein Rb, releasing transcription factor E2F to induce genes for DNA replication enzymes, nucleotide biosynthesis, and replication licensing factors such as Cdc6. DNA damage in G1 would risk copying lesions, necessitating arrest. Tumor suppressor p53 serves as guardian by acting as transcription factor stabilized upon ATM-CHK2 signaling after double-strand breaks. One of its principal targets is CDKN1A encoding p21CIP1/WAF1, a potent inhibitor of CDK2-cyclin

Ref: El-Deiry et al., Cell 1993, p21 as p53 Target; Bertoli et al., Nature Rev Mol Cell Biol 2013, G1-S Regulation.

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Cell Cycle Regulation

Which checkpoint prevents cells with damaged DNA from entering S phase?

Cell cycle progression in eukaryotes is guarded by surveillance mechanisms that halt advance when conditions are unfavorable. At transition from G1 to S phase, cell must ensure adequate size, nutrients, growth factor signaling, and integrity of genome before committing to DNA replication, an irreversible step that duplicates entire genetic content. G1 checkpoint, often termed restriction point in mammalian cells, integrates signals from cyclin D-CDK4/6 and cyclin E-CDK2 that phosphorylate retinoblastoma protein Rb, releasing E2F transcription factors driving S-phase genes. If DNA damage, oxida

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 17: Cell Cycle Control and Checkpoints; Sherr, Science 1996, G1 Progression.

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