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Department of Cell and Cancer Biology, Medicine Branch, National Cancer Institute, NIH, Rockville, Maryland 20850
Abstract
Several important signaling proteins including transcription factors and protein kinases depend on heat shock protein (Hsp)-90 for stability. p210bcr-abl, a protein expressed in chronic myelogenous leukemia, is functionally inhibited by the benzoquinone ansamycin herbimycin A. Benzoquinone ansamycins also bind to and inhibit the activity of Hsp90. We now demonstrate that p210bcr-abl is complexed with Hsp90 and its cochaperone p23 in K562 chronic myelogenous leukemia cells. Brief exposure to the benzoquinone ansamycin Hsp90 inhibitor geldanamycin (GA) decreases the association of p210bcr-abl with Hsp90 and p23 and increases its association with the chaperones Hsp70 and p60Hop. GA has a similar effect on chaperone association with v-src, another Hsp90-dependent oncogenic kinase. Loss of Hsp90/p23 association and acquisition of Hsp70/p60Hop association of both p210bcr-abl and v-src precede GA-induced degradation of these kinases. GA-induced degradation is mediated by the proteasome because proteasome inhibitors block the effects of GA, causing both p210bcr-abl and v-src to accumulate in a detergent-insoluble cellular fraction. Both p210bcr-abl and v-src are more susceptible to GA-induced degradation than are their normal cellular counterparts, c-abl and c-src.
Introduction
Hsp902
is a very abundant and ubiquitously expressed chaperone protein that
accounts for 1–2% of total cellular protein in unstressed mammalian
cells (1)
. It is highly conserved and is thought to be
essential for eukaryotic cell viability (2)
. A number of
proteins require interaction with Hsp90 and its cochaperones to acquire
a mature conformation that is, in turn, a prerequisite for proper
protein function. Such proteins include transcription factors, such as
steroid hormone receptors (3–5)
, the retinoid and aryl
hydrocarbon receptors (6)
, mutated p53 (7)
,
and hypoxia-inducible factor 1
(8)
and a number
of protein kinases such as v-src (9, 10)
, v-fps, v-fes
(11)
, v-yes, lck (12)
, Raf-1 (13, 14)
, Wee1 (15)
, casein kinase II (16)
,
and cyclin-dependent kinase 4 (17)
.
Protein kinases have long provided important models to study Hsp90 function. A multimolecular complex between v-src and a protein of 90 kDa was described as early as 1981 (9, 10) . Later it was shown that the 90 kDa protein bound to v-src is Hsp90 (5) and that v-src forms complexes with this chaperone in reticulocyte lysate as well as in whole cells (18) . The functional significance of v-src-Hsp90 association was not fully appreciated until the identification of benzoquinone ansamycins as specific small molecule Hsp90 antagonists (19) , although earlier experiments in yeast expressing regulatable levels of Hsp90 had demonstrated a chaperone requirement for v-src activity in this organism (20) .
The significance of benzoquinone ansamycins as biological modifiers first became apparent when herbimycin A was shown to revert the morphological phenotype of v-src-transformed cells (21, 22) . In due course, effects of this drug on other tyrosine kinases (23) , including p210bcr-abl (24) , were also described, leading to the frequent use of herbimycin A as a general tyrosine kinase inhibitor (25) . When Whitesell et al. (19) analyzed the effect of herbimycin A and the closely related benzoquinone ansamycin GA on v-src-expressing 3T3 fibroblasts, they noticed a discrepancy between the powerful ability of these drugs to inhibit v-src kinase activity in a cell culture model and their rather weak effect when used as direct kinase inhibitors in an in vitro kinase assay system. These authors then identified Hsp90 as a prominent benzoquinone ansamycin-binding protein, and they described the ability of these drugs to disrupt the complex between v-src and Hsp90, resulting in destabilization of v-src protein and its eventual loss from treated cells. This observation led to the identification of benzoquinone ansamycins as the first class of Hsp90 small molecule inhibitors, and these drugs have since become an important tool in the study of Hsp90 function (26) .
Since these initial reports, it has become apparent that Hsp90 participates in at least two multimolecular chaperone complexes that then associate with client proteins. One such complex comprises Hsp90, p23, and p50 (immunophilin in the case of steroid receptors), and the other consists of Hsp90, Hsp70, and p60Hop. Participation of Hsp90 in these complexes is conformationally regulated by nucleotide binding to its NH2 terminus (for review, see Refs. 27 and 28 ). Whereas association of client proteins with a p23-containing Hsp90 complex correlates with functionality, association with a complex containing Hsp70 and p60Hop may not. Benzoquinone ansamycins disrupt the former complex but stabilize the latter, giving rise to the possibility that the frequently observed instability of Hsp90 client proteins induced by GA may be secondary to a switch in composition of the associated chaperone complex from Hsp90/p23/p50 to Hsp90/Hsp70/p60Hop.
With these questions in mind, we have now examined the effects of GA on p210bcr-abl and v-src in more detail. p210bcr-abl is an oncogenic fusion protein expressed in CML, with a smaller variant also expressed in some cases of acute lymphocytic leukemia (29–31) . Fusion of a portion of the bcr gene to the abl-encoded tyrosine kinase results in constitutively elevated and deregulated tyrosine kinase activity in CML cells. Neither p210bcr-abl nor its normal counterpart c-abl have been previously reported to be associated with Hsp90, although effects of herbimycin A on p210bcr-abl activity have been described, and the inhibitory effects of benzoquinone ansamycins on cell culture and animal models of CML have been reported previously (24, 32–35) . We now show that p210bcr-abl associates with an Hsp90/p23 chaperone complex in K562 CML cells and that GA treatment causes destabilization of this kinase, secondary to disruption of its Hsp90 association and acquisition of association with an Hsp70/p60Hop chaperone complex, in a manner similar to the drug’s effects on chaperone complex association with v-src.
Results
Treatment of K562 Cells with GA Leads to Altered Composition of
Hsp90-containing Multimolecular Complexes that Associate with
p210bcr-abl and v-src.
To study p210bcr-abl, we used K562, a CML cell line that
expresses p210bcr-abl (36)
. After treatment
with GA for 1 h, a time at which little change in the steady-state
level of p210bcr-abl can be detected (see Fig. 2A
), K562 cells were lysed, and p210bcr-abl was
immunoprecipitated. Associated proteins were analyzed by immunoblotting
(Fig. 1A
). In untreated cells, Hsp90 and its cochaperone p23 were found to be
associated with p210bcr-abl, whereas levels of
coprecipitated Hsp70 and p60Hop were difficult to detect.
Within 1 h of GA treatment, the amount of Hsp90 and p23
coprecipitated with p210bcr-abl was greatly reduced,
whereas Hsp70 and p60Hop could now be readily found as part
of a p210bcr-abl multimolecular complex.
|
|
). After immunoprecipitating v-src, we analyzed coprecipitated proteins by
immunoblotting (Fig. 1B
). In untreated cells, Hsp90, p23,
Hsp70, and p60Hop were all coprecipitated with v-src. GA
treatment somewhat increased the amount of Hsp70 and p60Hop
associated with v-src, whereas the level of associated Hsp90 was
decreased, and p23 was lost from the v-src multimolecular complex after
1 h of exposure to GA. At no time did GA affect the stead-state
level of Hsp90, Hsp70, p23 or p60Hop in total cell lysate
(data not shown).
Longer Exposure to GA Causes Destabilization of
p210bcr-abl and v-src.
A number of proteins have been found to exist in multimolecular
complexes containing Hsp90 (39)
. Treatment with Hsp90
inhibitors such as GA or radicicol leads to proteolytic degradation of
most of these proteins (7, 19, 40)
. Thus, we analyzed the
kinetics of the effect of GA treatment on the steady-state level of
p210bcr-abl in K562 cells. Cells were treated with GA (2
µM) for various time intervals. p210bcr-abl
protein declined significantly after 3 h of GA treatment, and the
protein was difficult to detect after 8 h (Fig. 2A
). In
comparison, v-src was also greatly reduced in GA-treated TSv-src3T3
cells after 6 h of drug treatment.
p210bcr-abl and v-src Are Degraded by the Proteasome
after GA Treatment.
We expected p210bcr-abl to be degraded by the proteasome in
GA-treated cells, as has been described previously for several receptor
tyrosine kinases and Raf-1 (41, 42)
. To test this
hypothesis, we treated K562 cells with GA in the presence of several
protease inhibitors, including lysosomal, proteasomal, and calpain
inhibitors. Only the proteasome inhibitors LLnL and PS341 significantly
inhibited degradation of p210bcr-abl in GA-treated cells.
As reported previously for Raf-1 (42)
, the
p210bcr-abl protein protected from degradation was
insoluble in buffers containing only nonionic detergents but could be
solubilized in SDS-containing buffer (Fig. 3A
). Treatment with proteasome inhibitors alone (especially LLnL) led to a
moderate decrease in p210bcr-abl in the detergent-soluble
fraction concomitant with an increase of the protein in the insoluble
fraction. Inhibitors of the lysosome such as ammonium chloride and
bafilomycin had no significant protective effect against GA-induced
degradation of p210bcr-abl, nor did they alter the
detergent solubility of the protein.
|
). Once again, the protected protein could not be found in
the NP40-soluble fraction but only in pellets remaining after NP40
extraction that were resolubilized with SDS. In these resolubilized
pellet fractions, a ladder of v-src-reactive bands of increasing
molecular weight was observed, consistent with polyubiquitination of
v-src in these samples, as has been described for other proteins
extracted from cells after treatment with GA and proteasome inhibitors
(43, 44) .
The Cellular Proteins c-abl and c-src Are Less Sensitive to
Treatment with the Hsp90 Inhibitor GA than Their Mutated Counterparts.
p210bcr-abl and v-src are mutated proteins that cause
cellular transformation. We compared their normal cellular
counterparts, c-abl and c-src, in terms of susceptibility to GA
treatment. HL60 cells that express c-abl but not
p210bcr-abl and PC3 cells that express c-src but not v-src
were treated with GA (2 µM) for various time intervals.
The cells were lysed, and these proteins were analyzed by
immunoblotting (Fig. 4)
. Although some decrease in protein level could be seen after prolonged
exposure to GA, these proteins are more stable to GA treatment than are
mutated counterparts (compare with Fig. 1
). Several attempts to
coprecipitate c-abl and c-src with Hsp90 were not successful,
consistent with the decreased sensitivity of these proteins to GA. The
activity of GA in both HL60 and PC3 cells was demonstrated by
documenting loss of Raf-1 protein in both cell types after 12–16 h of
drug exposure, equivalent to the sensitivity of Raf-1 to GA in both
K562 and TSv-src3T3 cells (data not shown).
|
Benzoquinone ansamycins, particularly herbimycin A, were first described as general tyrosine kinase inhibitors, and herbimycin A has direct kinase inhibitory activity in some in vitro systems (23, 45) . Nevertheless, these drugs, particularly GA, are now used primarily as Hsp90 inhibitors. The first report of the effects of GA on the v-src-Hsp90 complex suggested a disruption of this protein-protein interaction (19) . Later studies, mostly based on steroid hormone receptors reconstituted in reticulocyte lysate, developed the concept that GA inhibits the transition from an immature Hsp90-p60Hop-Hsp70 complex to a complex including Hsp90-p23-immunophilin (or p50 in the case of several kinases) that allows the chaperoned protein to acquire a functional and perhaps stable conformation (46, 47) . Although the function of the Hsp90-Hsp70-p60Hop complex remains vague, it has been proposed to mediate proteolytic degradation of its associated client protein [i.e., steroid receptor or kinase (48) ]. Because there is a dynamic equilibrium between these complexes, a block of transition from one status to the other will eventually result in most of the chaperoned protein existing in one complex. GA binds to an ATP/ADP binding pocket that is located in the NH2-terminal domain of Hsp90 and serves as a switch domain regulating chaperone conformation (49, 50) . By blocking ATP binding to Hsp90, GA inhibits p23 and p50 binding while stabilizing Hsp70 and p60Hop association with Hsp90, and this appears to be a key mechanism by which the drug inhibits Hsp90 function (27) .
In this study, we found p210bcr-abl to be in a stable complex with Hsp90 in K562 cells. Coprecipitation experiments revealed that the Hsp90 complex bound to p210bcr-abl to also contained the cochaperone p23, whereas the presence of Hsp70 and p60Hop was difficult to detect. This demonstrates that most of the p210bcr-abl protein in untreated K562 cells exists in the mature Hsp90 complex. In contrast, v-src immunoprecipitates contained significant amounts of Hsp70 and p60Hop along with Hsp90 and p23, indicating that both mature and immature Hsp90-v-src complexes coexist at significant levels in untreated cells. Because the half-life of p210bcr-abl is in excess of 24 h (51, 52) , whereas the half-life of v-src in TSv-src3T3 cells is approximately 90 min,3 the degree of association of each kinase with the 2 Hsp90-containing chaperone complexes is consistent with the kinases’ markedly different stability under control conditions. We were able to demonstrate that composition of the multichaperone complexes associated with both p210bcr-abl and v-src was altered by GA before destabilization of these kinases, so that p23 association was lost, and Hsp70/p60Hop association was either increased or unaffected. Although the apparent loss of Hsp90 association concurrent with elevated or unchanged Hsp70/p60Hop association after GA treatment might at first glance appear to be counterintuitive, in the Hsp90-Hsp70-p60Hop complex, it is probably Hsp70 that directly contacts the client protein. Increased hydrophobicity of Hsp90 in the conformation associating with Hsp70 makes Hsp90 coprecipitation in this complex more detergent-sensitive than when it is bound to p23 (in which case Hsp90 contacts the client protein directly).
The mechanism of action of benzoquinone ansamycins on p210bcr-abl was thought to be through direct binding of these compounds to reactive SH groups in the kinase, resulting in inhibition of enzyme activity (32, 45) . We now offer an alternative explanation for the effects of at least some benzoquinone ansamycins, particularly GA, on p210bcr-abl. Treatment with GA leads to a rapid change in the Hsp90-containing multimolecular complexes associated with this kinase. The change in composition of protein kinase-chaperone multimolecular complexes that can be detected within 1 h of GA treatment is followed by a rapid decline in the steady-state level of p210bcr-abl. The decrease in both p210bcr-abl and v-src levels after GA treatment is mediated by the proteasome, as has been reported for other proteins similarly destabilized by benzoquinone ansamycins (41, 42) . As has been shown for Raf-1 but not for receptor tyrosine kinases, both p210bcr-abl and v-src targeted for degradation become insoluble in nonionic detergent after GA treatment if the proteasome is inhibited. It is thus reasonable to conclude that whereas the Hsp90-p23 chaperone complex is able to stabilize both kinases in soluble form, the Hsp90-Hsp70-p60Hop chaperone complex is unable to do so.
Comparison of the GA sensitivity of wild-type proteins c-src and c-abl with that of their mutated oncogenic counterparts v-src and p210bcr-abl shows that the mutated proteins are more susceptible to GA-induced degradation then the normal cellular proteins. Thus, the mutated proteins must be more dependent on Hsp90-p23 association for their stability and function and more sensitive to Hsp70-p60Hop-mediated proteasome targeting. In the case of c-src, an interaction between c-src and Hsp90 has been difficult to detect (19, 20, 53) , whereas v-src and especially its temperature-sensitive mutant exist in a very stable complex with Hsp90 (9) . We have also been unable to detect c-abl association with Hsp90 in HL60 cells.3
Whether the primary role of Hsp90 is to exert a protective function toward its client proteins (19, 40, 53) , or whether the chaperone instead potentiates the degradation of misfolded (e.g., mutant) proteins as a quality control mechanism (48) has been a matter of speculation. As our data suggest, Hsp90 may participate in both processes, depending on the multichaperone complex in which it is found. The Hsp70-p60Hop-Hsp90 complex binds to hydrophobic areas of partially folded proteins. After folding is completed, the client protein associates with a Hsp90-p23 complex, which stabilizes a labile conformation of the protein that is necessary for its function (e.g., binding to a steroid hormone in the case of a steroid hormone receptor). If the folding is not successful or if Hsp90-p23 complex formation is prevented by GA, the client protein remains complexed with Hsp70-p60Hop-Hsp90 and is eventually targeted to the proteasome for degradation. It remains to be determined whether proteasome targeting requires that the Hsp70-p60Hop-Hsp90 complex remains associated with the client protein. This hypothesis integrates the findings of various studies on the effects of GA on Hsp90 function, and it may also explain why some mutated proteins that achieve less stabile conformations compared with their wild-type counterparts might be more susceptible to the disruptive effects of Hsp90 inhibitors.
In conclusion, we offer evidence that p210bcr-abl inhibition by benzoquinone ansamycins is based on the fact that mature p210bcr-abl requires association with Hsp90 and its cochaperone p23 to maintain solubility and stability. In the presence of GA, the kinase instead associates preferentially with a Hsp70-p60Hop complex that favors its proteasome-mediated degradation. A similar hypothesis can explain the mechanism by which GA destabilizes v-src, a well-described example of an Hsp90-dependent and GA-sensitive kinase.
Materials and Methods
Cells, Antibodies, and Reagents.
K562 CML cells were obtained from the American Type Culture Collection
(Manassas, VA) and cultured in DMEM with 10% FCS and 10 mM
HEPES. Temperature-sensitive v-src-transfected NIH3T3
fibroblasts (TSv-src-3T3 cells) were maintained as described previously
(37)
. Antibodies used were the src-specific mAb 327
(Oncogene Science, Uniondale, NY), anti-Hsp90 and anti-Hsp70 mAbs
(SPA-830 and SPA-810, respectively; StressGen Biotechnologies,
Victoria, British Columbia, Canada), rabbit polyclonal anti-Hsp86
(mouse homologue of human Hsp90; NeoMarkers, Fremont, CA), and
anti-c-abl (AB-2 and AB-3, Calbiochem, San Diego, CA).
p60Hop mAb F5 was provided by D. Smith (Mayo Clinic,
Phoenix, AZ), and p23 mAb was provided by D. Toft (Mayo Clinic,
Rochester, MN). GA was obtained from the Developmental Therapeutics
Program, National Cancer Institute. PS-341 was provided by Dr. P.
Elliott (Proscript, Cambridge, MA). Lactacystin was purchased from Dr.
E. J. Corey (Harvard University, Cambridge, MA). LLnL, LLM, LLL,
chloroquine, ammonium chloride, bafilomycin, leupeptin, and
phenylmethylsulfonyl fluoride were obtained from Sigma (St. Louis, MO).
Other chemicals were of highest available grade.
Immunoprecipitation and Immunoblotting.
Subconfluent cells were rinsed with cold PBS and then lysed on ice in
TNESV lysis buffer [50 mM Tris-HCl (pH 7.5), 2
mM EDTA, 1% NP40, 100 mM NaCl, and 10
mM orthovanadate] supplemented with protease inhibitors (1
mM phenylmethylsulfonyl fluoride, 20 mg/ml leupeptin, and
20 mg/ml aprotinin) and 20 mM sodium molybdate. Lysates
were scraped, transferred into microtubes, and centrifuged at
16,000 x g for 20 min at 4°C. For detergent-free
lysis, we used a lysis buffer containing 10 mM Tris-HCl (pH
7.5), 1 mM MgCl2, and Tween 20 (0.2%, v/v)
supplemented with protease inhibitors and sodium molybdate. Cells were
scraped, homogenized in a tight-fitting Dounce homogizer, and sonicated
twice for 5 s with a 1 min incubation on ice before
centrifugation. Protein concentrations were determined by the
bicinchoninic acid method (Pierce, Rockford, IL). We used 25 µg of
total protein per condition for Western blots and 1 mg of total protein
for immunoprecipitations. To resolubilize denatured protein from cell
lysates, cells were lysed in TENSV buffer supplemented with 5
mM N-ethylmaleimide. After lysis and
centrifugation, the remaining pellet was extracted with SDS buffer
[2% SDS, 100 mM DTT, 80 mM Tris-HCl (pH 6.8),
10% glycerol]. The pellet was mechanically disrupted using a pipette
tip, and the extraction included two heating periods of 5 min at
95°C.
Acknowledgments
We thank Drs. D. Smith and D. Toft for supplying antibodies to p60Hop and p23, respectively.
Footnotes
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 To whom requests for reprints should be
addressed, at Department of Cell and Cancer Biology, Medicine Branch,
National Cancer Institute, NIH, Rockville, MD 20850. Phone (301)
402-3128, extension 318; Fax: (301) 402-4422; E-mail: len{at}helix.nih.gov 
2 The abbreviations used are: Hsp, heat shock
protein; GA, geldanamycin; CML, chronic myelogenous leukemia; mAb,
monoclonal antibody; LLnL, N-acetyl-Leu-norleucinal; LLM,
N-acetyl-Leu-Leu-normethioninal; LLL, N-CBZ-Leu-Leu-leucinal.
Received for publication 2/ 3/00. Revision received 5/23/00. Accepted for publication 5/29/00.
References
domain. Cell, 78: 787-798, 1994.[Medline]
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|
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|
|
|
|
 |
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
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|
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|
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|
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|
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K. Petersen Shay, Z. Wang, P.-x. Xing, I. F.C. McKenzie, and N. S. Magnuson Pim-1 Kinase Stability Is Regulated by Heat Shock Proteins and the Ubiquitin-Proteasome Pathway Mol. Cancer Res., March 1, 2005; 3(3): 170 - 181. [Abstract] [Full Text] [PDF]
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R. D. Unwin, D. W. Sternberg, Y. Lu, A. Pierce, D. G. Gilliland, and A. D. Whetton Global Effects of BCR/ABL and TEL/PDGFR{beta} Expression on the Proteome and Phosphoproteome: IDENTIFICATION OF THE RHO PATHWAY AS A TARGET OF BCR/ABL J. Biol. Chem., February 25, 2005; 280(8): 6316 - 6326. [Abstract] [Full Text] [PDF]
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 J. Sun and J. K. Liao Induction of Angiogenesis by Heat Shock Protein 90 Mediated by Protein Kinase Akt and Endothelial Nitric Oxide Synthase Arterioscler. Thromb. Vasc. Biol., December 1, 2004; 24(12): 2238 - 2244. [Abstract] [Full Text] [PDF]
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 H. Fujiwara, T. Yamakuni, M. Ueno, M. Ishizuka, T. Shinkawa, T. Isobe, and Y. Ohizumi IC101 Induces Apoptosis by Akt Dephosphorylation via an Inhibition of Heat Shock Protein 90-ATP Binding Activity Accompanied by Preventing the Interaction with Akt in L1210 Cells J. Pharmacol. Exp. Ther., September 1, 2004; 310(3): 1288 - 1295. [Abstract] [Full Text] [PDF]
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 A. Giannini and M.-J. Bijlmakers Regulation of the Src Family Kinase Lck by Hsp90 and Ubiquitination Mol. Cell. Biol., July 1, 2004; 24(13): 5667 - 5676. [Abstract] [Full Text] [PDF]
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H. Zhang, W. Wu, Y. Du, S. J. Santos, S. E. Conrad, J. T. Watson, N. Grammatikakis, and K. A. Gallo Hsp90/p50cdc37 Is Required for Mixed-lineage Kinase (MLK) 3 Signaling J. Biol. Chem., May 7, 2004; 279(19): 19457 - 19463. [Abstract] [Full Text] [PDF]
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P. Bonvini, H. D. Rosa, N. Vignes, and A. Rosolen Ubiquitination and Proteasomal Degradation of Nucleophosmin-Anaplastic Lymphoma Kinase Induced by 17-Allylamino-Demethoxygeldanamycin: Role of the Co-Chaperone Carboxyl Heat Shock Protein 70-Interacting Protein Cancer Res., May 1, 2004; 64(9): 3256 - 3264. [Abstract] [Full Text] [PDF]
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