Skip to content
Login Register

#cyclin

3 public questions tagged with this topic.

Cell Cycle Regulation

Which cyclin accumulates in S phase to promote DNA replication?

Orderly appearance and destruction of cyclins dictates CDK activation windows. Mitogenic stimulation through receptor tyrosine kinases activates Ras-MAPK cascade leading to transcription factor AP-1, Myc, and beta-catenin mediated induction of cyclin D1, D2, D3 genes. Cyclin D proteins accumulate throughout G1, assembling with CDK4 and CDK6 kinases whose activity requires mitogen-dependent stabilization and CAK phosphorylation. Cyclin D-CDK4/6 complexes phosphorylate retinoblastoma proteins at early sites, initiating limited E2F release and transcription of cyclin E. Cyclin E-CDK2 then complet

Ref: Bertoli et al., Nature Reviews Mol Cell Biol 2013, Cyclin Control. Alberts 7th ed., Chapter 17.

View Details
Cell Cycle Regulation

Which cyclin accumulates in S phase and promotes DNA replication?

Cyclin abundance oscillates generating waves of CDK activity. Cyclin D induced by mitogens drives early G1 progression, Cyclin E peaks at G1/S boundary initiating replication, then declines rapidly through SCF-Fbw7 mediated degradation after autophosphorylation. Cyclin A accumulates as cells enter and progress through S phase, reaching maximum in G2. Binding partners shift: in S phase, Cyclin A preferentially complexes with CDK2 phosphorylating components for continued DNA synthesis, E2F-dependent transcription termination, centrosome duplication and prevention of origin relicensing such as Cd

Ref: Murray, Cyclins and Cell Cycle Regulation, Cell Cycle Textbook; Alberts et al., Molecular Biology of the Cell, Chapter 17, S-Phase Cyclins.

View Details
Cell Cycle Regulation

What is the function of the SCF complex?

Ordered progression through interphase depends on timely degradation of regulatory proteins via ubiquitination. The SCF complex, meaning Skp1-Cullin-F-box, is a modular cullin-RING E3 ligase active from late G1 to early M. Core components include scaffold Cullin1, adaptor Skp1, RING finger Rbx1 and interchangeable F-box protein conferring substrate specificity. Canonical function involves CDK inhibitor p27 Kip1. When Cyclin E-CDK2 phosphorylates p27 at Thr187, phosphodegron is recognized by F-box protein Skp2 together with accessory Cks1, leading to Lys48-linked polyubiquitination and proteaso

Ref: Cardozo & Pagano, SCF Ubiquitin Ligases and Cell Cycle Control, Nat Rev Mol Cell Biol 2004; NCBI, SCF Functions.

View Details