Destruction of Xenopus cyclins A and B2, but not B1, requires binding to p34cdc2.

Stewart, Elspeth; Kobayashi, Hideki; Harrison, David K.; Hunt, Tim

doi:10.1002/j.1460-2075.1994.tb06296.x

Cited by 110 publications

(95 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…28 The NcoI fragment of Skp2 in pUHD-P1 was excised and transferred to the T7b1-FLAG vector, which is a variant of T7b1 vector. 29 The NotI fragment of the FLAG-Skp2 from T7b1-FLAG-Skp2 was transferred to pCAGGS-Pac, which is a variant of the pCAGGS vector 30 with a puromycin-resistant marker driven by SV40 early promoter.…”

Section: Methodsmentioning

confidence: 99%

Troglitazone induces p27Kip1-associated cell-cycle arrest through down-regulating Skp2 in human hepatoma cells

et al. 2003

View full text Add to dashboard Cite

Increasing evidence has confirmed that ligands for peroxisome proliferator-activated receptor ␥ (PPAR␥) exhibit antitumoral effects through inhibition of cell proliferation and induction of cell differentiation in several malignant neoplasms. Recently, we have documented the accumulation of a cyclin-dependent kinase inhibitor, p27 Kip1 , as well as an unexpected accumulation in cyclin E in G1-arrested human hepatoma cells treated with the PPAR␥ ligand troglitazone. Simultaneous accumulations in both p27 Kip1 and cyclin E are known to be characteristic phenotypes in cells derived from mice lacking Skp2, an F-box protein component of the SCF ubiquitin-ligase complex. Thus, the aim of the present study was to assess whether Skp2 might be involved in the down-regulation of p27 Kip1 in troglitazone-treated human hepatoma cells. A striking decrease in Skp2 expression and a reciprocal increase in p27 Kip1 expression were found in troglitazonetreated hepatoma cells but not in those cells treated with other PPAR␥ ligands such as pioglitazone and ciglitazone. Quantitative real-time RT-PCR analysis showed that troglitazone downregulated Skp2 at the mRNA levels. Consistently, ectopic overexpression in Skp2 brought resistance to troglitazone, resulting in a decreased population of arrested cells at the G1 phase compared with that in the mock-transfected cells. In surgically resected hepatocellular carcinoma (HCC) tissue, an increased expression in Skp2 was found in both the moderately differentiated HCCs and the poorly differentiated HCCs. In conclusion, troglitazone attenuated Skp2 expression, thereby promoting p27 Kip1 accumulation in human hepatoma cells. This therapeutic potential of the ligand may lead to new cell-cycle-based antitumor strategies for advanced HCCs.

show abstract

Section: Methodsmentioning

confidence: 99%

Troglitazone induces p27Kip1-associated cell-cycle arrest through down-regulating Skp2 in human hepatoma cells

et al. 2003

View full text Add to dashboard Cite

show abstract

“…The proteasome is able to remodel these complexes by degrading specific subunits without affecting other components [42,43]. For example, several steps in the cell cycle are controlled by the degradation of cyclins while they are bound to cyclindependent kinase subunit [44] or the degradation of cdk inhibitor while it is bound to the cyclin cdk complex [36]. The removal of the cyclin stops the kinase from functioning until a new cyclin binds whereas degradation of the inhibitor releases the kinase activity of the cyclin cdk complex.…”

Section: A Second Step In Ubiquitin-dependent Proteasome Targetingmentioning

confidence: 99%

Protein targeting to ATP-dependent proteases

Inobe

Matouschek

2008

Current Opinion in Structural Biology

View full text Add to dashboard Cite

ATP-dependent proteases control diverse cellular processes by degrading specific regulatory proteins. Understanding how these regulatory proteins are targeted to ATP-dependent proteases is of central importance to understanding their biological role as regulators. Recent work has shown that protein substrates are specifically transferred to ATP-dependent proteases through different routes. These routes can function in parallel or independently. In all of these targeting mechanisms it can be useful to separate two steps: substrate binding to the protease and initiation of degradation.To be active, newly synthesized protein chains must fold into three-dimensional structures, but regulated unfolding is also critically important in some biological processes, such as protein degradation by ATP-dependent proteases and protein translocation across membranes [1]. Unfolding is required during degradation because the proteolytic sites of the ATP-dependent proteases are sequestered deep inside the proteases' structures and accessible only through narrow openings. Similarly, unfolding is required during several translocation processes because the protein import channels in some organelles are not wide enough for native proteins to fit through them. The mechanisms of unfolding in both types of processes are similar to each other but different from that of unfolding induced by heat or chemical denaturants. Here we discuss how the requirement for protein unfolding during degradation affects the way ATPdependent proteases select their substrates. ATP-dependent proteasesATP-dependent proteases degrade short-lived regulatory proteins and thereby control cellular processes such as signal transduction, cell cycle, and gene transcription. The proteases also clear misfolded and aggregated proteins from the cell and produce some of the peptides to be displayed at cell surface as part of adaptive immune response. In eukaryotes, these functions are performed mainly by the proteasome. In prokaryotes and the organelles of eukaryotes, the functions are fulfill by analogues of the proteasome, such as the ClpAP, ClpXP, HslUV, FtsH, and Lon proteases. Although ATP-dependent proteases show only relatively little sequence identity, they share a common architecture [2].The ATP-dependent proteases all form large multisubunit particles (Figure 1). In the simplest case, FtsH protease, the particle consists 6 copies of a 71 kDa subunit forming a complex of approximately 425 kDa, and in the most complex case, the proteasome, the particle consists of some 40 different subunits forming a complex of 2 MDa molecular weight [3,4]. The subunits are mostly arranged in six or seven subunit rings that stack on top of each other to

show abstract

“…11,18 Since cyclin A contains a similar D-box, it is likely that cyclin A is also degraded by APC/C. [19][20][21][22] Furthermore, microinjection of antibodies against the APC/C components suppresses cyclin A degradation, 10 and APC/C CDC20 or APC/C CDH1 can promote cyclin A ubiquitination in vitro. 10,12 Although cyclin A associates with the SCF SKP2 complex, we found no evidence that links SCF SKP2 to cyclin A ubiquitination.…”

Section: Introductionmentioning

confidence: 99%

The N-terminal Regulatory Domain of Cyclin A Contains Redundant Ubiquitination Targeting Sequences and Acceptor Sites

Fung

Yam²,

Poon³

2005

Cell Cycle

View full text Add to dashboard Cite

ACKNOWLEDGEMENTSWe are grateful for Jane Endicott, Tim Hunt and Michele Pagano for generous gifts of reagents. We thank members of the Poon Lab for constructive criticism on the manuscript. This work was supported in part by the Research Grants Council grants HKUST6135/03M and the HKUST grant HIA03/ 04.SC01 to R.Y.C.P.. ReportThe N-Terminal Regulatory Domain of Cyclin A Contains Redundant Ubiquitination Targeting Sequences and Acceptor Sites ABSTRACT Cyclin A is destroyed during mitosis by the ubiquitin-proteasome system. Like cyclin B, a destruction box (D-box) motif is required for the destruction of cyclin A. However, cyclin A degradation is more complicated than cyclin B because cyclin A's D-box motif is more extensive and proteolysis involves complex signaling in some organisms. In this study, we found that in addition to the D-box, the region between residues 123-157 also contributed to the ubiquitination and degradation of human cyclin A. Indeed, removal of the bulk of the N-terminal regulatory domain was needed to completely stabilize cyclin A and eliminate ubiquitination. A putative second RxxL motif around residue 138 played only a minor role in cyclin A degradation. To distinguish between sequences recognized by the ubiquitination machinery and the ubiquitin acceptor sites per se, we utilized a novel approach involving in vitro cleavage of cyclin A after ubiquitination. We found that several lysine residues proximal to the D-box (Lys37, Lys54 and Lys68) were ubiquitin acceptor sites. Cyclin A lacking the three lysine residues was degraded slower than the wild-type protein. Although these lysines were normally used, ubiquitination could shift to other cryptic sites when the preferred sites were unavailable, suggesting the exact positions of the ubiquitin chains also contributed to degradation. Together, these data revealed that ubiquitination does not occur randomly on cyclin A and open up questions on the precise function of the D-box.

show abstract

Destruction of Xenopus cyclins A and B2, but not B1, requires binding to p34cdc2.

Cited by 110 publications

References 47 publications

Troglitazone induces p27Kip1-associated cell-cycle arrest through down-regulating Skp2 in human hepatoma cells

Troglitazone induces p27Kip1-associated cell-cycle arrest through down-regulating Skp2 in human hepatoma cells

Protein targeting to ATP-dependent proteases

The N-terminal Regulatory Domain of Cyclin A Contains Redundant Ubiquitination Targeting Sequences and Acceptor Sites

Contact Info

Product

Resources

About