Cell division control protein 4

Last updated
Cdc4
Cdc4 structure.jpg
Crystal structure of Cdc4
Identifiers
SymbolCdc4
Alt. symbolscell division control protein 4
NCBI gene 850539
UniProt P07834
Search for
Structures Swiss-model
Domains InterPro

Cdc4 (cell division control protein 4) is a substrate recognition component of the SCF (SKP1-CUL1-F-box protein) ubiquitin ligase complex, which acts as a mediator of ubiquitin transfer to target proteins, leading to their subsequent degradation via the ubiquitin-proteasome pathway. Cdc4 targets primarily cell cycle regulators for proteolysis. It serves the function of an adaptor that brings target molecules to the core SCF complex. Cdc4 was originally identified in the model organism Saccharomyces cerevisiae . CDC4 gene function is required at G1/S and G2/M transitions during mitosis and at various stages during meiosis. [1]

Contents

Homologues

The human homologue of the cdc4 gene is called FBXW7. The corresponding gene product is the F-box/WD repeat-containing protein 7.[ citation needed ]

F-box/WD repeat-containing protein 7
Identifiers
SymbolFbw7
Alt. symbolsF-box and WD-40 domain-containing protein 7, F-box protein FBX30, Archipelago homolog (hAgo), SEL-10, hCdc4
UniProt Q969H0
Search for
Structures Swiss-model
Domains InterPro

In the nematode C. elegans, the homologue to Cdc4 is F-box/WD repeat-containing protein sel-10.

F-box/WD repeat-containing protein sel-10
Identifiers
SymbolF-box/WD repeat-containing protein sel-10
Alt. symbolsSuppressor/enhancer of lin-12 protein 10 Egg laying defective protein 41
UniProt Q93794
Search for
Structures Swiss-model
Domains InterPro

Some general features

Cdc4 has a molecular weight of 86'089Da, an isoelectric point of 7.14, and consists of 779 amino acids. It resides exclusively in the nucleus because of a single monopartite nuclear localisation sequence (NLS) comprising amino acids 82-85 in the N-terminal domain. [2]

Structure

Cdc4 is one component of the E3 complex SCF (CDC4), which comprises CDC53, SKP1, RBX1, and CDC4. Its 779 amino acids (in S. cerevisiae) are arranged into one F-box domain (approximately 40 amino acids ("F-box" motif)) and 7 WD repeats. [3]

Cdc4 is a WD-40 repeat F-box protein. Like all members of this family, it contains a conserved dimerization motif called D domain. In yeast Cdc4, the D domain protomers arrange in a superhelical homodimeric manner. SCF (Cdc4) dimerization hardly affects the affinity for target molecules, but significantly increases ubiquitin conjugation. Cdc4 adapts a suprafacial configuration: The substrate-binding sites lie in the same plane AS the catalytic sites, with a separation of 64Å within and 102Å between each SCF monomer. [4] In Cdc4, the substrate binding domain is built on WD40 domains, which use repeats of 40 amino acids), each forming four anti-parallel beta-strands, to assemble the blades of a so-called beta-propeller. Beta-propellers are a quite frequent form of adaptable surface for interaction between different proteins. This substrate interaction region is located C-terminally. [5] There are three isoforms of Cdc4 in mammals: α, β, and γ. These are produced via alternative splicing of 3 unique 5’ exons to 10 common 3’ exons. This results in proteins that differ only at their N-termini. [6]

Cdc4 protein interacts with Cdc34, an ubiquitin-conjugating enzyme, and Cdc53 in vivo. (There is a Cdc4p/Cdc53p-binding region on Cdc34p.) All three proteins are stable throughout the cell cycle. [7]

Function

Fig. 1 The figure shows a sketch of how the SCF complex functions, and what the role of Cdc4 is within this structure (-> adaptor function). SCF(Cdc4) fig1.jpg
Fig. 1 The figure shows a sketch of how the SCF complex functions, and what the role of Cdc4 is within this structure (-> adaptor function).

Various cellular regulatory mechanisms heavily depend on ubiquitin-dependent degradation. The SCF (Cdc4) complex has a regulatory function in cell cycle progression, signal transduction, and transcription. [8] In order for the cell cycle to proceed, several inhibitory proteins, as well as cyclins, have to be eliminated at given time points. Cdc4 assists there by recruiting target molecules via its C-terminal substrate interaction domain (WD40 repeat domain) to the ubiquitination machinery. This causes transfer of ubiquitin molecules to the target, hence marks it for degradation. Cdc4 recognizes and binds to phosphorylated target proteins.[ citation needed ]

Cdc4 can be essential, or nonessential, depending on the organism. For instance, it is essential in S. cerevisiae , while it is non-essential in C. albicans. It is essential for initiation of DNA replication and separation of spindle pole bodies, hence for the formation of the poles of the mitotic spindle. In budding yeast it is also involved in bud development, fusion of zygotic nuclei (karyogamy) after conjugation, and several aspects of sporulation. Roughly speaking, in the cell cycle Cdc4 function is required for G1/S and G2/M transition.[ citation needed ]

Some important interactions in which Cdc4 is involved are:

Onset of S-phase

Swi5 is a transcriptional activator of Sic1, which inhibits S-phase CDKs. Thus, Sic1 protein degradation is necessary to enter S-phase. SCF (Cdc4) complex’s regulatory function concerning S-phase entry comprises not only degradation of Sic1, but also degradation of Swi5. [8] In order for the substrate adapter unit Cdc4 to bind to Sic1, a minimum of any six of the nine cyclin-dependent kinase sites on Sic1 have to be phosphorylated. In other words: There is a threshold number of phosphorylation sites in order to achieve receptor-ligand binding. As recently stated, this "suggests that the ultrasensitivity in the Sic1-Cdc4 system may be driven at least in part by cumulative electrostatic interactions". [9] In general, an ultrasensitive enzyme requires less than 81-fold increase in stimulus to drive it from 10% to 90% activity. "Ultrasensitivity" highlights that the upstroke of the stimulus/response curve is steeper than the one that is obtained for a hyperbolic Michaelis-Menten enzyme. [10] Thus, ultrasensitivity allows a highly sensitive response: A graded input can be transformed into a sharply thresholded output. The development of B-type cyclin–cyclin-dependent kinase activity, as well as the onset of DNA replication, requires degradation of Sic1 in the late G1 phase of the cell cycle. The WD domain of Cdc4 binds to the phosphorylated form of Sic1. Each bond to a Sic1-Phosphate is weak, but together the binding is strong enough to enable Sic1-degradation via the pathway described before. Hence, in this case ultrasensitivity allows precise definition ("fine tuning") of the time point in which destruction of Sic1 occurs, leading to initiation of the next step in the cell cycle (-> DNA replication). [9]

G2/M transition

Up until now it is not satisfyingly understood how Cdc4 triggers G2-M transition. In general, the second degradation complex involved in cell cycle progression, APC, is responsible for proteolysis at that stage. However, experimental data suggests that Cdc4 function in G2/M transition may be linked to the degradation of Pds1 (anaphase inhibitor). And what is more, CDC4 and CDC20, an activator of APC, interact genetically. [11]

Cdc4 recruits several other substrates than Sic1 to the SCF core complex, including the Cln-Cdc28 inhibitor / cytoskeletal scaffold protein Far1, the transcription factor Gcn4, and the replication protein Cdc6. In addition to those functions mentioned above, Cdc4 is involved in some other degradation-dependent events in S. cerevisiae like for instance unfolded protein response. [12]

Clinical significance

In mammals, amongst others c-Myc, Src3, Cyclin E, and the Notch intracellular domain are substrates of Cdc4. Due to its involvement in degradation of various cell cycle regulators, as well as several compounds of signaling pathways (e.g. Notch), Cdc4 is a highly sensible component of every organism in which it functions. The cdc4 gene is a haplo-insufficient tumor suppressor gene. Knock-out of this gene in mice leads to an embryonic lethal phenotype. CDC4 mutations occur in a number of cancer types. They are described best in colorectal tumors, and also have been found to be a mutational target in pancreatic cancer. [13]

E3 has an additional function to its primary role in the degradation of certain cell cycle regulators: It is also involved in formation of the neural crest. Hence, Cdc4 is a protein "with separable but complementary functions in control of cell proliferation and differentiation". [6] This evokes the assumption -beyond regulating cell cycle progression- Cdc4 as a tumor suppressor protein may extend its ability to directly regulate tissue differentiation. However, its concrete role in diseases is still to be elucidated.[ citation needed ]

See also

Related Research Articles

<span class="mw-page-title-main">Anaphase-promoting complex</span> Cell-cycle regulatory complex

Anaphase-promoting complex is an E3 ubiquitin ligase that marks target cell cycle proteins for degradation by the 26S proteasome. The APC/C is a large complex of 11–13 subunit proteins, including a cullin (Apc2) and RING (Apc11) subunit much like SCF. Other parts of the APC/C have unknown functions but are highly conserved.

<span class="mw-page-title-main">Ubiquitin ligase</span> Protein

A ubiquitin ligase is a protein that recruits an E2 ubiquitin-conjugating enzyme that has been loaded with ubiquitin, recognizes a protein substrate, and assists or directly catalyzes the transfer of ubiquitin from the E2 to the protein substrate. In simple and more general terms, the ligase enables movement of ubiquitin from a ubiquitin carrier to another thing by some mechanism. The ubiquitin, once it reaches its destination, ends up being attached by an isopeptide bond to a lysine residue, which is part of the target protein. E3 ligases interact with both the target protein and the E2 enzyme, and so impart substrate specificity to the E2. Commonly, E3s polyubiquitinate their substrate with Lys48-linked chains of ubiquitin, targeting the substrate for destruction by the proteasome. However, many other types of linkages are possible and alter a protein's activity, interactions, or localization. Ubiquitination by E3 ligases regulates diverse areas such as cell trafficking, DNA repair, and signaling and is of profound importance in cell biology. E3 ligases are also key players in cell cycle control, mediating the degradation of cyclins, as well as cyclin dependent kinase inhibitor proteins. The human genome encodes over 600 putative E3 ligases, allowing for tremendous diversity in substrates.

<span class="mw-page-title-main">SCF complex</span>

Skp, Cullin, F-box containing complex is a multi-protein E3 ubiquitin ligase complex that catalyzes the ubiquitination of proteins destined for 26S proteasomal degradation. Along with the anaphase-promoting complex, SCF has important roles in the ubiquitination of proteins involved in the cell cycle. The SCF complex also marks various other cellular proteins for destruction.

<span class="mw-page-title-main">Cyclin-dependent kinase 2</span> Protein-coding gene in the species Homo sapiens

Cyclin-dependent kinase 2, also known as cell division protein kinase 2, or Cdk2, is an enzyme that in humans is encoded by the CDK2 gene. The protein encoded by this gene is a member of the cyclin-dependent kinase family of Ser/Thr protein kinases. This protein kinase is highly similar to the gene products of S. cerevisiae cdc28, and S. pombe cdc2, also known as Cdk1 in humans. It is a catalytic subunit of the cyclin-dependent kinase complex, whose activity is restricted to the G1-S phase of the cell cycle, where cells make proteins necessary for mitosis and replicate their DNA. This protein associates with and is regulated by the regulatory subunits of the complex including cyclin E or A. Cyclin E binds G1 phase Cdk2, which is required for the transition from G1 to S phase while binding with Cyclin A is required to progress through the S phase. Its activity is also regulated by phosphorylation. Multiple alternatively spliced variants and multiple transcription initiation sites of this gene have been reported. The role of this protein in G1-S transition has been recently questioned as cells lacking Cdk2 are reported to have no problem during this transition.

<span class="mw-page-title-main">Cyclin-dependent kinase 1</span> Mammalian protein found in Homo sapiens

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. 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. With its cyclin partners, Cdk1 forms complexes that phosphorylate a variety of target substrates ; phosphorylation of these proteins leads to cell cycle progression.

<span class="mw-page-title-main">SKP2</span> Protein-coding gene in the species Homo sapiens

S-phase kinase-associated protein 2 is an enzyme that in humans is encoded by the SKP2 gene.

<span class="mw-page-title-main">CDC20</span> Protein-coding gene in the species Homo sapiens

The cell division cycle protein 20 homolog is an essential regulator of cell division that is encoded by the CDC20 gene in humans. To the best of current knowledge its most important function is to activate the anaphase promoting complex (APC/C), a large 11-13 subunit complex that initiates chromatid separation and entrance into anaphase. The APC/CCdc20 protein complex has two main downstream targets. Firstly, it targets securin for destruction, enabling the eventual destruction of cohesin and thus sister chromatid separation. It also targets S and M-phase (S/M) cyclins for destruction, which inactivates S/M cyclin-dependent kinases (Cdks) and allows the cell to exit from mitosis. A closely related protein, Cdc20homologue-1 (Cdh1) plays a complementary role in the cell cycle.

<span class="mw-page-title-main">BTRC (gene)</span> Protein-coding gene in the species Homo sapiens

F-box/WD repeat-containing protein 1A (FBXW1A) also known as βTrCP1 or Fbxw1 or hsSlimb or pIkappaBalpha-E3 receptor subunit is a protein that in humans is encoded by the BTRC gene.

<span class="mw-page-title-main">FBXW7</span> Protein-coding gene in the species Homo sapiens

F-box/WD repeat-containing protein 7 is a protein that in humans is encoded by the FBXW7 gene.

<span class="mw-page-title-main">CDC34</span> Protein-coding gene in the species Homo sapiens

CDC34 is a gene that in humans encodes the protein Ubiquitin-conjugating enzyme E2 R1. This protein is a member of the ubiquitin-conjugating enzyme family, which catalyzes the covalent attachment of ubiquitin to other proteins.

<span class="mw-page-title-main">CKS1B</span> Protein-coding gene in the species Homo sapiens

Cyclin-dependent kinases regulatory subunit 1 is a protein that in humans is encoded by the CKS1B gene.

<span class="mw-page-title-main">FBXW11</span> Protein-coding gene in the species Homo sapiens

βTrCP2 is a protein that in humans is encoded by the FBXW11 gene.

<span class="mw-page-title-main">FBXW2</span> Protein-coding gene in the species Homo sapiens

F-box/WD repeat-containing protein 2 is a protein that in humans is encoded by the FBXW2 gene.

<span class="mw-page-title-main">Cullin</span> Hydrophobic scaffold protein

Cullins are a family of hydrophobic scaffold proteins which provide support for ubiquitin ligases (E3). All eukaryotes appear to have cullins. They combine with RING proteins to form Cullin-RING ubiquitin ligases (CRLs) that are highly diverse and play a role in myriad cellular processes, most notably protein degradation by ubiquitination.

Sic1, a protein, is a stoichiometric inhibitor of Cdk1-Clb complexes in the budding yeast Saccharomyces cerevisiae. Because B-type cyclin-Cdk1 complexes are the drivers of S-phase initiation, Sic1 prevents premature S-phase entry. Multisite phosphorylation of Sic1 is thought to time Sic1 ubiquitination and destruction, and by extension, the timing of S-phase entry.

<span class="mw-page-title-main">Wee1</span>

Wee1 is a nuclear kinase belonging to the Ser/Thr family of protein kinases in the fission yeast Schizosaccharomyces pombe. Wee1 has a molecular mass of 96 kDa and is a key regulator of cell cycle progression. It influences cell size by inhibiting the entry into mitosis, through inhibiting Cdk1. Wee1 has homologues in many other organisms, including mammals.

A series of biochemical switches control transitions between and within the various phases of the cell cycle. The cell cycle is a series of complex, ordered, sequential events that control how a single cell divides into two cells, and involves several different phases. The phases include the G1 and G2 phases, DNA replication or S phase, and the actual process of cell division, mitosis or M phase. During the M phase, the chromosomes separate and cytokinesis occurs.

<span class="mw-page-title-main">APC/C activator protein CDH1</span> Fungal protein found in Saccharomyces cerevisiae S288c

Cdh1 is one of the substrate adaptor protein of the anaphase-promoting complex (APC) in the budding yeast Saccharomyces cerevisiae. Functioning as an activator of the APC/C, Cdh1 regulates the activity and substrate specificity of this ubiquitin E3-ligase. The human homolog is encoded by the FZR1 gene, which is not to be confused with the CDH1 gene.

<span class="mw-page-title-main">G2-M DNA damage checkpoint</span>

The G2-M DNA damage checkpoint is an important cell cycle checkpoint in eukaryotic organisms that ensures that cells don't initiate mitosis until damaged or incompletely replicated DNA is sufficiently repaired. Cells with a defective G2-M checkpoint will undergo apoptosis or death after cell division if they enter the M phase before repairing their DNA. The defining biochemical feature of this checkpoint is the activation of M-phase cyclin-CDK complexes, which phosphorylate proteins that promote spindle assembly and bring the cell to metaphase.

<span class="mw-page-title-main">Motifs targeted by APC/C</span>

The anaphase- promoting complex or cyclosome (APC/C) is a highly specific ubiquitin protein ligase responsible for triggering events of late mitosis. In early mitosis, Cdc20 levels rise and APC/C binds to form active APC/CCdc20. This then leads to the destruction of mitotic cyclins, securin, and other proteins to trigger chromosome separation in anaphase. In early anaphase, Cdk1 is inactivated, leading to the activation of Cdh1, the other activator subunit of APC/C. This then triggers the degradation of Cdc20 and leads to the activation of APC/CCdh1 through G1 to suppress S- phase cyclin-Cdk activity. At the end of G1, APC/CCdh1 is inactivated and S- phase and mitotic cyclins gets reaccumulate as the cell progresses to S phase.

References

  1. ↑ Simchen G, Hirschberg J (May 1977). "Effects of the mitotic cell-cycle mutation cdc4 on yeast meiosis". Genetics. 86 (1): 57–72. doi:10.1093/genetics/86.1.57. PMC   1213672 . PMID   328339.
  2. ↑ Blondel M, Galan JM, Chi Y, Lafourcade C, Longaretti C, Deshaies RJ, Peter M (Nov 2000). "Nuclear-specific degradation of Far1 is controlled by the localization of the F-box protein Cdc4". The EMBO Journal. 19 (22): 6085–97. doi:10.1093/emboj/19.22.6085. PMC   305831 . PMID   11080155.
  3. ↑ "Human Cdc4 / Fbw7 / HSel 10 peptide (Ab12311) is not available".
  4. ↑ Tang X, Orlicky S, Lin Z, Willems A, Neculai D, Ceccarelli D, Mercurio F, Shilton BH, Sicheri F, Tyers M (Jun 2007). "Suprafacial orientation of the SCFCdc4 dimer accommodates multiple geometries for substrate ubiquitination". Cell. 129 (6): 1165–76. doi: 10.1016/j.cell.2007.04.042 . PMID   17574027. S2CID   14050047.
  5. ↑ Orlicky S, Tang X, Willems A, Tyers M, Sicheri F (Jan 2003). "Structural basis for phosphodependent substrate selection and orientation by the SCFCdc4 ubiquitin ligase" (PDF). Cell. 112 (2): 243–56. doi: 10.1016/S0092-8674(03)00034-5 . PMID   12553912. S2CID   13032437.
  6. 1 2 Almeida AD, Wise HM, Hindley CJ, Slevin MK, Hartley RS, Philpott A (2010). "The F-box protein Cdc4/Fbxw7 is a novel regulator of neural crest development in Xenopus laevis". Neural Development. 5: 1. doi:10.1186/1749-8104-5-1. PMC   2819241 . PMID   20047651.
  7. ↑ Mathias N, Steussy CN, Goebl MG (Feb 1998). "An essential domain within Cdc34p is required for binding to a complex containing Cdc4p and Cdc53p in Saccharomyces cerevisiae". The Journal of Biological Chemistry. 273 (7): 4040–5. doi: 10.1074/jbc.273.7.4040 . PMID   9461595.
  8. 1 2 Kishi T, Ikeda A, Koyama N, Fukada J, Nagao R (Sep 2008). "A refined two-hybrid system reveals that SCF(Cdc4)-dependent degradation of Swi5 contributes to the regulatory mechanism of S-phase entry". Proceedings of the National Academy of Sciences of the United States of America. 105 (38): 14497–502. Bibcode:2008PNAS..10514497K. doi: 10.1073/pnas.0806253105 . PMC   2567208 . PMID   18787112.
  9. 1 2 Borg M, Mittag T, Pawson T, Tyers M, Forman-Kay JD, Chan HS (Jun 2007). "Polyelectrostatic interactions of disordered ligands suggest a physical basis for ultrasensitivity". Proceedings of the National Academy of Sciences of the United States of America. 104 (23): 9650–5. Bibcode:2007PNAS..104.9650B. doi: 10.1073/pnas.0702580104 . PMC   1887549 . PMID   17522259.
  10. ↑ Huang CY, Ferrell JE (Sep 1996). "Ultrasensitivity in the mitogen-activated protein kinase cascade". Proceedings of the National Academy of Sciences of the United States of America. 93 (19): 10078–83. Bibcode:1996PNAS...9310078H. doi: 10.1073/pnas.93.19.10078 . PMC   38339 . PMID   8816754.
  11. ↑ Goh PY, Surana U (Aug 1999). "Cdc4, a protein required for the onset of S phase, serves an essential function during G(2)/M transition in Saccharomyces cerevisiae". Molecular and Cellular Biology. 19 (8): 5512–22. doi:10.1128/mcb.19.8.5512. PMC   84393 . PMID   10409741.
  12. ↑ Pal B, Chan NC, Helfenbaum L, Tan K, Tansey WP, Gething MJ, et al. (Feb 2007). "SCFCdc4-mediated degradation of the Hac1p transcription factor regulates the unfolded protein response in Saccharomyces cerevisiae" (PDF). Molecular Biology of the Cell. 18 (2): 426–40. doi:10.1091/mbc.E06-04-0304. PMC   1783797 . PMID   17108329.
  13. ↑ Calhoun ES, Jones JB, Ashfaq R, Adsay V, Baker SJ, Valentine V, Hempen PM, Hilgers W, Yeo CJ, Hruban RH, Kern SE (Oct 2003). "BRAF and FBXW7 (CDC4, FBW7, AGO, SEL10) mutations in distinct subsets of pancreatic cancer: potential therapeutic targets". The American Journal of Pathology. 163 (4): 1255–60. doi:10.1016/S0002-9440(10)63485-2. PMC   1868306 . PMID   14507635.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.