Biology:Cyclin-dependent kinase 1

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Short description: Mammalian protein found in Homo sapiens


A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example

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 protein kinase, and is a key player in cell cycle regulation.[1] 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.[2] 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.[3]

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, CDK1, shares approximately 63% amino-acid identity with its yeast homolog. Furthermore, human CDK1 is capable of rescuing fission yeast carrying a cdc2 mutation.[4][5] 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.[6]

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.[1]

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.[7] 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;[8] 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 APCCdc20, 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.[9] 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.[10] 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

  1. ↑ 1.0 1.1 Morgan, David L. (2007). The cell cycle: principles of control. London: New Science Press. pp. 30–31. ISBN 978-0-19-920610-0. 
  2. ↑ "Control of the yeast cell cycle by the Cdc28 protein kinase". Curr. Opin. Cell Biol. 5 (2): 166–179. April 1993. doi:10.1016/0955-0674(93)90099-C. PMID 8507488. 
  3. ↑ "An overview of Cdk1-controlled targets and processes". Cell Division 5 (11): 11. May 2010. doi:10.1186/1747-1028-5-11. PMID 20465793. 
  4. ↑ Lee, Melanie; Nurse, Paul (Jun 1987). "Complementation used to clone a human homologue of the fission yeast cell cycle control gene cdc2". Nature 327 (6117): 31–35. doi:10.1038/327031a0. PMID 3553962. Bibcode: 1987Natur.327...31L. 
  5. ↑ "Crystal structure of cyclin-dependent kinase 2". Nature 363 (6430): 595–602. June 1993. doi:10.1038/363595a0. PMID 8510751. Bibcode: 1993Natur.363..595D. 
  6. ↑ "Mechanism of CDK activation revealed by the structure of a cyclinA-CDK2 complex". Nature 376 (6538): 313–320. July 1995. doi:10.1038/376313a0. PMID 7630397. Bibcode: 1995Natur.376..313J. 
  7. ↑ "Positive feedback of G1 cyclins ensures coherent cell cycle entry". Nature 454 (7202): 291–296. July 2008. doi:10.1038/nature07118. PMID 18633409. Bibcode: 2008Natur.454..291S. 
  8. ↑ "Specialization and targeting of B-type cyclins". Mol Cell 4 (1): 11–19. July 1999. doi:10.1016/S1097-2765(00)80183-5. PMID 10445023. 
  9. ↑ "The structural basis for specificity of substrate and recruitment peptides for cyclin-dependent kinases". Nat. Cell Biol. 1 (7): 438–443. November 1999. doi:10.1038/15674. PMID 10559988. 
  10. ↑ "Cell cycle checkpoints: preventing an identity crisis". Science 274 (5293): 1664–1672. December 1996. doi:10.1126/science.274.5293.1664. PMID 8939848. Bibcode: 1996Sci...274.1664E. 
  11. ↑ "Microtubule-targeting drugs induce bcl-2 phosphorylation and association with Pin1". Neoplasia 3 (6): 550–9. 2001. doi:10.1038/sj.neo.7900213. PMID 11774038. 
  12. ↑ "Microtubule-targeting drugs induce Bcl-2 phosphorylation and association with Pin1". Neoplasia 3 (1): 70–9. 2001. doi:10.1038/sj.neo.7900131. PMID 11326318. 
  13. ↑ 13.0 13.1 "Cyclin E associates with BAF155 and BRG1, components of the mammalian SWI-SNF complex, and alters the ability of BRG1 to induce growth arrest". Mol. Cell. Biol. 19 (2): 1460–9. February 1999. doi:10.1128/mcb.19.2.1460. PMID 9891079. 
  14. ↑ "Isolation of a human cyclin cDNA: evidence for cyclin mRNA and protein regulation in the cell cycle and for interaction with p34cdc2". Cell 58 (5): 833–846. September 1989. doi:10.1016/0092-8674(89)90936-7. PMID 2570636. 
  15. ↑ "Cyclin F regulates the nuclear localization of cyclin B1 through a cyclin-cyclin interaction". EMBO J. 19 (6): 1378–1388. March 2000. doi:10.1093/emboj/19.6.1378. PMID 10716937. 
  16. ↑ "Formation and activation of a cyclin E-cdk2 complex during the G1 phase of the human cell cycle". Science 257 (5077): 1689–1694. September 1992. doi:10.1126/science.1388288. PMID 1388288. Bibcode: 1992Sci...257.1689K. 
  17. ↑ "KAP: a dual specificity phosphatase that interacts with cyclin-dependent kinases". Proc. Natl. Acad. Sci. U.S.A. 91 (5): 1731–1735. March 1994. doi:10.1073/pnas.91.5.1731. PMID 8127873. Bibcode: 1994PNAS...91.1731H. 
  18. ↑ "Cdi1, a human G1 and S phase protein phosphatase that associates with Cdk2". Cell 75 (4): 791–803. November 1993. doi:10.1016/0092-8674(93)90498-F. PMID 8242750. 
  19. ↑ "Cell cycle-dependent phosphorylation of Disabled-2 by cdc2". Oncogene 22 (29): 4524–4530. July 2003. doi:10.1038/sj.onc.1206767. PMID 12881709. 
  20. ↑ "Yeast two-hybrid screens imply involvement of Fanconi anemia proteins in transcription regulation, cell signaling, oxidative metabolism, and cellular transport". Exp. Cell Res. 289 (2): 211–221. October 2003. doi:10.1016/S0014-4827(03)00261-1. PMID 14499622. 
  21. ↑ "The Fanconi anemia polypeptide, FAC, binds to the cyclin-dependent kinase, cdc2". Blood 90 (3): 1047–54. August 1997. doi:10.1182/blood.V90.3.1047. PMID 9242535. 
  22. ↑ "Association with Cdc2 and inhibition of Cdc2/Cyclin B1 kinase activity by the p53-regulated protein Gadd45". Oncogene 18 (18): 2892–2900. May 1999. doi:10.1038/sj.onc.1202667. PMID 10362260. 
  23. ↑ "The GADD45 inhibition of Cdc2 kinase correlates with GADD45-mediated growth suppression". J. Biol. Chem. 275 (22): 16602–16608. June 2000. doi:10.1074/jbc.M000284200. PMID 10747892. 
  24. ↑ "Identification of a functional domain in a GADD45-mediated G2/M checkpoint". J. Biol. Chem. 275 (47): 36892–36898. November 2000. doi:10.1074/jbc.M005319200. PMID 10973963. 
  25. ↑ "GADD45b and GADD45g are cdc2/cyclinB1 kinase inhibitors with a role in S and G2/M cell cycle checkpoints induced by genotoxic stress". J. Cell. Physiol. 192 (3): 327–338. September 2002. doi:10.1002/jcp.10140. PMID 12124778. 
  26. ↑ "Human homologue of the Drosophila melanogaster lats tumour suppressor modulates CDC2 activity". Nat. Genet. 21 (2): 177–181. February 1999. doi:10.1038/5960. PMID 9988268. 
  27. ↑ "Activation of Src-like p56/p53lyn tyrosine kinase by ionizing radiation". J. Biol. Chem. 269 (32): 20739–43. August 1994. doi:10.1016/S0021-9258(17)32054-9. PMID 8051175. 
  28. ↑ "The protein-tyrosine kinase Lck associates with and is phosphorylated by Cdc2". J. Biol. Chem. 271 (44): 27517–27523. November 1996. doi:10.1074/jbc.271.44.27517. PMID 8910336. 
  29. ↑ "The C-terminal regulatory domain of p53 contains a functional docking site for cyclin A". J. Mol. Biol. 300 (3): 503–518. July 2000. doi:10.1006/jmbi.2000.3830. PMID 10884347. 
  30. ↑ "Downregulation of the cdc2/cyclin B protein kinase activity by binding of p53 to p34(cdc2)". Biochem. Biophys. Res. Commun. 283 (2): 507–512. May 2001. doi:10.1006/bbrc.2001.4792. PMID 11327730. 
  31. ↑ "Proteomic analysis of ubiquitinated proteins in normal hepatocyte cell line Chang liver cells". Proteomics 8 (14): 2885–2896. July 2008. doi:10.1002/pmic.200700887. PMID 18655026. 

Further reading

External links

  • Overview of all the structural information available in the PDB for UniProt: P06493 (Cyclin-dependent kinase 1) at the PDBe-KB.

de:Cyclin-abhängige Kinase 1#Die Entdeckung des cdc2-Gens



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