Cyclin-dependent kinase 1

CDK1
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 4YC6, 4Y72, 5HQ0, 4YC3
Identifiers
Aliases	CDK1, CDC2, CDC28A, P34CDC2, cyclin-dependent kinase 1, cyclin dependent kinase 1
External IDs	OMIM: 116940 MGI: 88351 HomoloGene: 68203 GeneCards: CDK1
Gene ontology Molecular function • transferase activity • nucleotide binding • protein kinase activity • histone kinase activity • kinase activity • Hsp70 protein binding • protein binding • RNA polymerase II carboxy-terminal domain kinase activity • ATP binding • protein serine/threonine kinase activity • chromatin binding • cyclin binding • cyclin-dependent protein kinase activity • cyclin-dependent protein serine/threonine kinase activity • virus receptor activity Cellular component • centrosome • membrane • spindle • nucleoplasm • microtubule organizing center • midbody • spindle microtubule • mitochondrion • mitotic spindle • extracellular exosome • cytoskeleton • nucleus • nuclear chromosome, telomeric region • cyclin-dependent protein kinase holoenzyme complex • cytoplasm • cytosol • mitochondrial matrix • endoplasmic reticulum membrane • cyclin B1-CDK1 complex Biological process • positive regulation of protein localization to nucleus • centrosome cycle • regulation of embryonic development • response to cadmium ion • positive regulation of protein import into nucleus, translocation • epithelial cell differentiation • response to organic cyclic compound • phosphorylation • protein complex assembly • response to copper ion • positive regulation of ubiquitin-protein ligase activity involved in regulation of mitotic cell cycle transition • positive regulation of mitotic cell cycle • negative regulation of apoptotic process • pronuclear fusion • regulation of ubiquitin-protein ligase activity involved in mitotic cell cycle • response to activity • regulation of Schwann cell differentiation • cell division • positive regulation of DNA replication • cell aging • DNA replication • histone phosphorylation • mitotic nuclear envelope disassembly • positive regulation of gene expression • positive regulation of cardiac muscle cell proliferation • activation of MAPK activity • chromosome condensation • G2/M transition of mitotic cell cycle • response to axon injury • peptidyl-serine phosphorylation • animal organ regeneration • response to organonitrogen compound • response to amine • DNA repair • cell cycle • anaphase-promoting complex-dependent catabolic process • microtubule cytoskeleton organization • response to ethanol • mitotic G2 DNA damage checkpoint • Golgi disassembly • peptidyl-threonine phosphorylation • cell migration • ventricular cardiac muscle cell development • response to toxic substance • response to hydrogen peroxide • response to drug • cellular response to hydrogen peroxide • protein localization to kinetochore • apoptotic process • protein ubiquitination involved in ubiquitin-dependent protein catabolic process • cell proliferation • proteasome-mediated ubiquitin-dependent protein catabolic process • negative regulation of ubiquitin-protein ligase activity involved in mitotic cell cycle • mitotic cell cycle • DNA damage response, signal transduction by p53 class mediator resulting in cell cycle arrest • regulation of gene expression • regulation of meiotic cell cycle • ciliary basal body docking • protein phosphorylation • positive regulation of G2/M transition of mitotic cell cycle • protein deubiquitination • mitotic cell cycle phase transition • positive regulation of mitochondrial ATP synthesis coupled electron transport • viral entry into host cell • regulation of G2/M transition of mitotic cell cycle Sources:Amigo / QuickGO
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	983	12534
Ensembl	ENSG00000170312	ENSMUSG00000019942
UniProt	P06493	P11440
RefSeq (mRNA)	NM_001130829 NM_001170406 NM_001170407 NM_001786 NM_033379 NM_001320918	NM_007659
RefSeq (protein)	NP_001163877 NP_001163878 NP_001307847 NP_001777 NP_203698	NP_031685
Location (UCSC)	Chr 10: 60.78 – 60.79 Mb	Chr 10: 69.34 – 69.35 Mb
PubMed search	[1]	[2]
Wikidata
View/Edit Human View/Edit Mouse

Cyclin-dependent kinase 1 also known as CDK1 or cell division cycle protein 2 homolog is a highly conserved protein that functions as a serine/threonine kinase, and is a key player in cell cycle regulation.^[3] It has been highly studied in the budding yeast S. cerevisiae, and the fission yeast S. pombe, where it is encoded by genes cdc28 and cdc2, respectively.^[4] In humans, Cdk1 is encoded by the CDC2 gene.^[5] With its cyclin partners, Cdk1 forms complexes that phosphorylate a variety of target substrates (over 75 have been identified in budding yeast); phosphorylation of these proteins leads to cell cycle progression.^[6]

Structure

Crystal Structure of the human Cdk1 homolog, Cdk2

Cdk1 is a small protein (approximately 34 kilodaltons), and is highly conserved. The human homolog of Cdk1, CDC2, shares approximately 63% amino-acid identity with its yeast homolog. Furthermore, human CDC2 is capable of rescuing fission yeast carrying a cdc2 mutation.^[5][7] Cdk1 is comprised mostly by the bare protein kinase motif, which other protein kinases share. Cdk1, like other kinases, contains a cleft in which ATP fits. Substrates of Cdk1 bind near the mouth of the cleft, and Cdk1 residues catalyze the covalent bonding of the γ-phosphate to the oxygen of the hydroxyl serine/threonine of the substrate.

In addition to this catalytic core, Cdk1, like other cyclin-dependent kinases, contains a T-loop, which, in the absence of an interacting cyclin, prevents substrate binding to the Cdk1 active site. Cdk1 also contains a PSTAIRE helix, which, upon cyclin binding, moves and rearranges the active site, facilitating Cdk1 kinase activities.^[8]

Function

Fig. 1 The diagram shows the role of Cdk1 in progression through the S. cerevisiae cell cycle. Cln3-Cdk1 leads to Cln1,2-Cdk1 activity, eventually resulting in Clb5,6-Cdk1 activity and then Clb1-4-Cdk1 activity.^[3]

When bound to its cyclin partners, Cdk1 phosphorylation leads to cell cycle progression. Cdk1 activity is best understood in S. cerevisiae, so Cdk1 S. cerevisiae activity is described here.

In the budding yeast, initial cell cycle entry is controlled by two regulatory complexes, SBF (SCB-binding factor) and MBF (MCB-binding factor). These two complexes control G₁/S gene transcription; however, they are normally inactive. SBF is inhibited by the protein Whi5; however, when phosphorylated by Cln3-Cdk1, Whi5 is ejected from the nucleus, allowing for transcription of the G₁/S regulon, which includes the G₁/S cyclins Cln1,2.^[9] G₁/S cyclin-Cdk1 activity leads to preparation for S phase entry (e.g., duplication of centromeres or the spindle pole body), and a rise in the S cyclins (Clb5,6 in S. cerevisiae). Clb5,6-Cdk1 complexes directly lead to replication origin initiation;^[10] however, they are inhibited by Sic1, preventing premature S phase initiation.

Cln1,2 and/or Clb5,6-Cdk1 complex activity leads to a sudden drop in Sic1 levels, allowing for coherent S phase entry. Finally, phosphorylation by M cyclins (e.g., Clb1, 2, 3 and 4) in complex with Cdk1 leads to spindle assembly and sister chromatid alignment. Cdk1 phosphorylation also leads to the activation of the ubiquitin-protein ligase APC^Cdc20, an activation which allows for chromatid segregation and, furthermore, degradation of M-phase cyclins. This destruction of M cyclins leads to the final events of mitosis (e.g., spindle disassembly, mitotic exit).

Regulation

Given its essential role in cell cycle progression, Cdk1 is highly regulated. Most obviously, Cdk1 is regulated by its binding with its cyclin partners. Cyclin binding alters access to the active site of Cdk1, allowing for Cdk1 activity; furthermore, cyclins impart specificity to Cdk1 activity. At least some cyclins contain a hydrophobic patch which may directly interact with substrates, conferring target specificity.^[11] Furthermore, cyclins can target Cdk1 to particular subcellular locations.

In addition to regulation by cyclins, Cdk1 is regulated by phosphorylation. A conserved tyrosine (Tyr15 in humans) leads to inhibition of Cdk1; this phosphorylation is thought to alter ATP orientation, preventing efficient kinase activity. In S. pombe, for example, incomplete DNA synthesis may lead to stabilization of this phosphorylation, preventing mitotic progression.^[12] Wee1, conserved among all eukaryotes phosphorylates Tyr15, whereas members of the Cdc25 family are phosphatases, counteracting this activity. The balance between the two is thought to help govern cell cycle progression. Wee1 is controlled upstream by Cdr1, Cdr2, and Pom1.

Cdk1-cyclin complexes are also governed by direct binding of Cdk inhibitor proteins (CKIs). One such protein, already discussed, is Sic1. Sic1 is a stoichiometric inhibitor that binds directly to Clb5,6-Cdk1 complexes. Multisite phosphorylation, by Cdk1-Cln1/2, of Sic1 is thought to time Sic1 ubiquitination and destruction, and by extension, the timing of S-phase entry. Only until Sic1 inhibition is overcome can Clb5,6 activity occur and S phase initiation may begin.

Interactions

Cdk1 has been shown to interact with:

See also

Mastl

References

Further reading