Tag: Cell cycle regulation

Post-translational modifications are essential regulators of cell-cycle progression. Learn how phosphorylation, ubiquitination, acetylation, SUMOylation, methylation, and other PTMs control CDKs, cyclins, checkpoints, DNA replication, mitosis, and protein degradation.

Timely protein degradation is essential for orderly cell-cycle progression. Explore key cell-cycle regulators, their degradation mechanisms, and how their turnover controls G1/S transition, mitosis, chromosome segregation and mitotic exit.

Mdm2 is a RING‑type E3 ubiquitin ligase that controls p53 stability through ubiquitination, nuclear export and proteasomal degradation. By interacting with p53, Mdmx/Mdm4 and ARF, Mdm2 regulates DNA‑damage responses, cell‑cycle progression and oncogenesis, making it a central determinant of tumour development and genome stability.

K48‑linked ubiquitination is the principal degradation signal in eukaryotic cells, directing proteins to the 26S proteasome. Built by E1, E2 and E3 enzymes, K48‑linked chains regulate protein turnover, cell‑cycle progression and DNA‑damage responses, forming a central mechanism for maintaining proteostasis and preventing toxic protein accumulation.

RING finger ubiquitin ligases are the largest class of E3 enzymes in the ubiquitin–proteasome system, defined by a zinc‑binding cross‑brace RING domain that positions E2~Ub for direct ubiquitin transfer. They regulate essential cellular processes including cell cycle progression, DNA repair, immunity, and neuronal function. Dysregulation of RING and RBR ligases such as MDM2 and Parkin contributes to cancer and neurodegeneration, while modern PROTAC therapeutics harness CRL4^CRBN and CRL2^VHL complexes to redirect ubiquitination toward disease‑associated proteins.