Search results for SKP2

Showing 24 results out of 51

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Protein (4 results from a total of 4)

Identifier: R-HSA-975554
Species: Homo sapiens
Compartment: nucleoplasm
Primary external reference: UniProt: SKP2: Q13309
Identifier: R-HSA-975495
Species: Homo sapiens
Compartment: cytosol
Primary external reference: UniProt: SKP2: Q13309
Identifier: R-HSA-9687073
Species: Homo sapiens
Compartment: nucleoplasm
Primary external reference: UniProt: SKP2: Q13309
Identifier: R-HSA-9661042
Species: Homo sapiens
Compartment: nucleoplasm
Primary external reference: UniProt: RB1: P06400

Interactor (2 results from a total of 2)

Identifier: Q13309-1
Species: Homo sapiens
Primary external reference: UniProt: Q13309-1
Identifier: Q13309-2
Species: Homo sapiens
Primary external reference: UniProt: Q13309-2

Reaction (6 results from a total of 27)

Identifier: R-HSA-9686969
Species: Homo sapiens
Compartment: nucleoplasm
RB1-dependent polyubiquitination of SKP2 by the APC/C:Cdh1 complex is an important mechanism of RB1-mediated cell cycle exit, which contributes to the RB1 tumor suppressive role. ABC/C:Cdh1-mediated polyubiquitination targets SKP2 for proteasome-mediated degradation. RB1 and APC/C:Cdh1-dependent degradation of SKP2 allows accumulation of CDKN1B (p27Kip1) in the cell, as CDKN1B is a target of the SKP2-containing SCF ubiquitin ligase complex. CDKN1B acts as a CDK inhibitor, enabling mitotic exit (Ji et al. 2004, Binne et al. 2007).
Identifier: R-HSA-188191
Species: Homo sapiens
Compartment: nucleoplasm
SKP2 is degraded by the anaphase promoting complex/Cyclosome and its activator FZR1 (Cdh1) [APC/C(Cdh1)] (Bashir et al, 2004; Wei et al, 2004). The tight regulation of APC/C(Cdh1) activity ensures the timely elimination SKP2 and, thus, plays a critical role in controlling the M/G1 transition (mitotic exit). APC/C:Cdh1-mediated degradation of SKP2 depends on RB1, as RB1 recruits SKP2 to the APC/C:Cdh1 complex, by simultaneously interacting with SKP2 and FZR1. RB1 does not undergo APC/C:Cdh1-mediated ubiquitination (Binne et al. 2007).
Identifier: R-HSA-9686980
Species: Homo sapiens
Compartment: nucleoplasm
The pocket domain of the RB1 tumor suppressor protein binds to the N-terminal domain of SKP2, a component of the SCF (SKP1-CUL1-F-box protein) E3 ubiquitin-protein ligase complex, whose targets include the cyclin-dependent kinase (CDK) inhibitor p27Kip1 (CDKN1B) (Ji et al. 2004, Binne et al. 2007). RB1 is able to simultanously interact with SKP2 and with FZR1 (Cdh1). FZR1 is a substrate-specific adapter for the anaphase promoting complex/cyclosome (APC/C). The interaction with FZR1 involves a different subregion of the pocket domain than the interaction with SKP2, and is partially dependent on the LxCxE binding cleft (Binne et al. 2007).
Identifier: R-HSA-9687377
Species: Homo sapiens
Compartment: cytosol
A tripartite complex formed between RB1, SKP2 and FZR1 (Cdh1) targets SKP2 for the anaphase promoting complex/cyclosome (APC/C:Cdh1)-mediated ubiquitination and subsequent proteasome-mediated degradation. Both SKP2 and FZR1 interact with the pocket domain of RB1, with amino acid residues 637–738 and 772–824 involved in SKP2 binding and the cleft region (amino acids 753–761), containing the LxCxE motif, involved in FZR1 binding (Binne et al. 2007). RB1 T738_R775del (RB1 Ex22del) cancer mutant, which lacks exon 22, is able to associate with SKP2 but unable to bind FZR1. This mutant is defective in inducing accumulation of CDKN1B (p27Kip1) and promoting mitotic exit as it cannot prevent SKP2-mediated ubiquitination and degradation of CDKN1B (Ji et al. 2004, Binne et al. 2007). RB1 T738_R775del mutant is also defective in E2F binding (Ji et al. 2004). RB1 missense mutant, RB1 R661W, which causes low penetrance familial retinoblastoma, is unable to bind to E2Fs but retains the ability to bind to SKP2 and FZR2 and to induce CDKN1B accumulation (Ji et al. 2004, Binne et al. 2007).
Identifier: R-HSA-8939706
Species: Homo sapiens
Compartment: nucleoplasm
The SCF(SKP2) E3 ubiquitin ligase complex polyubiquitinates RUNX2 on unknown lysine residues, targeting it for proteasome-mediated degradation. SKP2-triggered RUNX2 degradation negatively regulates osteogenesis by inhibiting differentiation of osteoblasts (Thacker et al. 2016). This process is inhibited by glucose uptake in osteoblasts (Wei et al. 2015).
Identifier: R-HSA-187545
Species: Homo sapiens
Compartment: nucleoplasm
The accessory protein, Cks1 promotes efficient interaction between phosphorylated p27 and the SCF (Skp2) complex (Ganoth et al., 2001; Spruck et al., 2001). Cks1 binds to Skp2 in the leucine-rich repeat (LRR) domain and C-terminal tail (Hao et al., 2005). The phosphorylated Thr187 side chain of p27 associates with a phosphate binding site on Cks1, and the side chain containing Glu185 is positioned in the interface between Skp2 and Cks1 where it interacts with both (Hao et al., 2005).

Complex (6 results from a total of 10)

Identifier: R-HSA-8939702
Species: Homo sapiens
Compartment: nucleoplasm
Identifier: R-HSA-187547
Species: Homo sapiens
Compartment: nucleoplasm
Identifier: R-HSA-187541
Species: Homo sapiens
Compartment: nucleoplasm
Identifier: R-HSA-8939693
Species: Homo sapiens
Compartment: nucleoplasm
Identifier: R-HSA-9686978
Species: Homo sapiens
Compartment: nucleoplasm
Identifier: R-HSA-9708443
Species: Homo sapiens
Compartment: nucleoplasm

Pathway (6 results from a total of 8)

Identifier: R-HSA-187577
Species: Homo sapiens
Compartment: nucleoplasm
During G1, the activity of cyclin-dependent kinases (CDKs) is kept in check by the CDK inhibitors (CKIs) p27 and p21, thereby preventing premature entry into S phase (see Guardavaccaro and Pagano, 2006). These two CKIs are degraded in late G1 phase by the ubiquitin pathway (Pagano et al., 1995; Bloom et al., 2003) involving the ubiquitin ligase SCF(Skp2) (Tsvetkov et al., 1999; Carrano et al., 1999; Sutterluty et al., 1999, Bornstein et al., 2003) and the cell-cycle regulatory protein Cks1 (Ganoth et al., 2001; Spruck et al 2001; Bornstein et al., 2003). Recognition of p27 by SCF(Skp2) and its subsequent ubiquitination is dependent upon Cyclin E/A:Cdk2- mediated phosphorylation at Thr 187 of p27 (Montagnoli et al., 1999). There is evidence that Cyclin A/B:Cdk1 complexes can also bind and phosphorylate p27 on Th187 (Nakayama et al., 2004). Degradation of polyubiquitinated p27 by the 26S proteasome promotes the activity of CDKs in driving cells into S phase. (Montagnoli et al., 1999; Tsvetkov et al., 1999, Carrano et al 1999). The mechanism of SCF(Skp2)-mediated degradation of p21 is similar to that of p27 in terms of its requirements for the presence of Cks1 and of Cdk2/cyclin E/A (Bornstein et al.,2003; Wang et al., 2005). In addition, as observed for p27, p21 phosphorylation at a specific site (Ser130) stimulates its ubiquitination. In contrast to p27, however, ubiquitination of p21 can take place in the absence of phosphorylation, although with less efficiency (Bornstein et al.,2003). SCF(Skp2)-mediated degradation of p27/p21 continues from late G1 through M-phase. During G0 and from early G1 to G1/S, Skp2 is degraded by the anaphase promoting complex/Cyclosome and its activator Cdh1 [APC/C(Cdh1)] (Bashir et al, 2004; Wei et al, 2004). The tight regulation of APC/C(Cdh1) activity ensures the timely elimination Skp2 and, thus, plays a critical role in controlling the G1/S transition. APC/C(Cdh1) becomes active in late M-phase by the association of unphosphorylated Cdh1 with the APC/C. APC/C(Cdh1) remains active until the G1/S phase at which time it interacts with the inhibitory protein, Emi1 (Hsu et al., 2002). Inhibition of APC/C(Cdh1) activity results in an accumulation of cyclins, which leads to the phosphorylation and consequently to a further inactivation of Cdh1 at G1/S (Lukas et al., 1999). Finally, to make the inactivation of APC/C(Cdh1) permanent, Cdh1 and its E2, namely Ubc10, are eliminated in an auto-ubiquitination event (Listovsky et al., 2004; Rape and Kirschner, 2004). At G1/S, Skp2 reaccumulates as Cdh1 is inactivated, thus allowing the ubiquitination of p21 and p27 and resulting in a further increase in CDK activity.
Identifier: R-HSA-69656
Species: Homo sapiens
Cyclin A:Cdk2 plays a key role in S phase entry by phosphorylation of proteins including Cdh1, Rb, p21 and p27. During G1 phase of the cell cycle, cyclin A is synthesized and associates with Cdk2. After forming in the cytoplasm, the Cyclin A:Cdk2 complexes are translocated to the nucleus (Jackman et al.,2002). Prior to S phase entry, the activity of Cyclin A:Cdk2 complexes is negatively regulated through Tyr 15 phosphorylation of Cdk2 (Gu et al., 1995) and also by the association of the cyclin kinase inhibitors (CKIs), p27 and p21. Phosphorylation of cyclin-dependent kinases (CDKs) by the CDK-activating kinase (CAK) is required for the activation of the CDK2 kinase activity (Aprelikova et al., 1995). The entry into S phase is promoted by the removal of inhibitory Tyr 15 phosphates from the Cdk2 subunit of Cyclin A:Cdk2 complex by the Cdc25 phosphatases (Blomberg and Hoffmann, 1999) and by SCF(Skp2)-mediated degradation of p27/p21 (see Ganoth et al., 2001). While Cdk2 is thought to play a primary role in regulating entry into S phase, recent evidence indicates that Cdk1 is equally capable of promoting entry into S phase and the initiation of DNA replication (see Bashir and Pagano, 2005). Thus, Cdk1 complexes may also play a significant role at this point in the cell cycle.
Identifier: R-HSA-9661069
Species: Homo sapiens
Compartment: nucleoplasm
This pathway describes impaired binding of RB1 pocket domain mutants to activating E2Fs, E2F1, E2F2 and E2F3 (Templeton et al. 1991, Helin et al. 1993, Otterson et al. 1997, Ji et al. 2004).
Identifier: R-HSA-8940973
Species: Homo sapiens
The complex of RUNX2 and CBFB regulates transcription of genes involved in differentiation of osteoblasts.
RUNX2 stimulates transcription of the BGLAP gene, encoding osteocalcin (Ducy and Karsenty 1995, Ducy et al. 1997). Binding of the RUNX2:CBFB complex to the BGLAP gene promoter is increased when RUNX2 is phosphorylated on serine residue S451 (Wee et al. 2002). Osteocalcin, a bone-derived hormone, is one of the most abundant non-collagenous proteins of the bone extracellular matrix (reviewed in Karsenty and Olson 2016). Association of the activated androgen receptor (AR) with RUNX2 prevents binding of RUNX2 to the BGLAP promoter (Baniwal et al. 2009). When YAP1, tyrosine phosphorylated by SRC and/or YES1, binds to RUNX2 at the BGLAP gene promoter, transcription of the BGLAP gene is inhibited (Zaidi et al. 2004). Signaling by SRC is known to inhibit osteoblast differentiation (Marzia et al. 2000).
Simultaneous binding of RUNX2 and SP7 (Osterix, also known as OSX) to adjacent RUNX2 and SP7 binding sites, respectively, in the UCMA promoter, synergistically activates UCMA transcription. UCMA stimulates osteoblast differentiation and formation of mineralized nodules (Lee et al. 2015).
The SCF(SKP2) E3 ubiquitin ligase complex inhibits differentiation of osteoblasts by polyubiquitinating RUNX2 and targeting it for proteasome-mediated degradation (Thacker et al. 2016). This process is inhibited by glucose uptake in osteoblasts (Wei et al. 2015).
Identifier: R-HSA-8939902
Species: Homo sapiens
Compartment: nucleoplasm
Several transcription factors have been implicated in regulation of the RUNX2 gene transcription. Similar to the RUNX1 gene, the RUNX2 gene expression can be regulated from the proximal P2 promoter or the distal P1 promoter (reviewed in Li and Xiao 2007).
Activated estrogen receptor alpha (ESR1) binds estrogen response elements (EREs) in the P2 promoter and stimulates RUNX2 transcription (Kammerer et al. 2013). Estrogen-related receptor alpha (ERRA) binds EREs or estrogen-related response elements (ERREs) in the P2 promoter of RUNX2. When ERRA is bound to its co-factor PPARG1CA (PGC1A), it stimulates RUNX2 transcription. When bound to its co-factor PPARG1CB (PGC1B), ERRA represses RUNX2 transcription (Kammerer et al. 2013).
TWIST1, a basic helix-loop-helix (bHLH) transcription factor, stimulates RUNX2 transcription by binding to the E1-box in the P2 promoter (Yang, Yang et al. 2011). TWIST proteins also interact with the DNA-binding domain of RUNX2 to modulate its activity during skeletogenesis (Bialek et al. 2004). Schnurri-3 (SHN3) is another protein that interacts with RUNX2 to decrease its availability in the nucleus and therefore its activity (Jones et al. 2006). In contrast, RUNX2 and SATB2 interact to enhance the expression of osteoblast-specific genes (Dobreva et al. 2006). Formation of the heterodimer with CBFB (CBF-beta) also enhances the transcriptional activity of RUNX2 (Kundu et al. 2002, Yoshida et al. 2002, Otto et al. 2002).
Transcription of RUNX2 from the proximal promoter is inhibited by binding of the glucocorticoid receptor (NR3C1) activated by dexamethasone (DEXA) to a glucocorticoid receptor response element (GRE), which is also present in the human promoter (Zhang et al. 2012).
NKX3-2 (BAPX1), required for embryonic development of the axial skeleton (Tribioli and Lufkin 1999), binds the distal (P1) promoter of the RUNX2 gene and inhibits its transcription (Lengner et al. 2005). RUNX2-P1 transcription is also autoinhibited by RUNX2-P1, which binds to RUNX2 response elements in the P1 promoter of RUNX2 (Drissi et al. 2000). In contrast, binding of RUNX2-P2 to the proximal P2 promoter autoactivates transcription of RUNX2-P2 (Ducy et al. 1999). Binding of a homeodomain transcription factor DLX5, and possibly DLX6, to the RUNX2 P1 promoter stimulates RUNX2 transcription (Robledo et al. 2002, Lee et al. 2005). The homeobox transcription factor MSX2 can bind to DLX5 sites in the promoter of RUNX2 and inhibit transcription of RUNX2-P1 (Lee et al. 2005).
Translocation of RUNX2 protein to the nucleus is inhibited by binding to non-activated STAT1 (Kim et al. 2003).
Several E3 ubiquitin ligases were shown to polyubiquitinate RUNX2, targeting it for proteasome-mediated degradation: FBXW7a (Kumar et al. 2015), STUB1 (CHIP) (Li et al. 2008), SMURF1 (Zhao et al. 2003, Yang et al. 2014), WWP1 (Jones et al. 2006), and SKP2 (Thacker et al. 2016).
Identifier: R-HSA-9687136
Species: Homo sapiens
RB1 regulates mitotic exit by acting on SKP2, a component of the SCF E3 ubiquitin ligase complex. RB1 facilitates degradation of SKP2 by the anaphase promoting complex/cyclosome (APC/C), thus preventing SKP2-mediated degradation of the cyclin-dependent kinase inhibitor CDKN1B (p27Kip1). RB1-dependent accumulation of p27Kip1 plays an important role in mitotic exit and RB1-mediated tumor suppression (reviewed by Dyson 2016).
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