Publications by authors named "Mari J Tokita"

13 Publications

  • Page 1 of 1

Biallelic loss of in a patient with pediatric medulloblastoma.

Cold Spring Harb Mol Case Stud 2019 10 23;5(5). Epub 2019 Oct 23.

Rady Children's Institute for Genomic Medicine, San Diego, California 92123, USA.

Genome sequencing was performed on matched normal and tumor tissue from a 6.5-yr-old boy with a diagnosis of recurrent medulloblastoma. A pathogenic heterozygous c.432+1G>A canonical splice donor site variant in was detected on analysis of blood DNA. Analysis of tumor DNA showed the same splice variant along with copy-neutral loss of heterozygosity on Chromosome 20 encompassing , consistent with predicted biallelic loss of in the tumor specimen. This case strengthens the evidence implicating as a tumor-suppressor gene in medulloblastoma and highlights a scenario in which therapeutics targeting the cAMP pathway may be of great utility.
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http://dx.doi.org/10.1101/mcs.a004572DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6824258PMC
October 2019

A clinical survey of mosaic single nucleotide variants in disease-causing genes detected by exome sequencing.

Genome Med 2019 07 26;11(1):48. Epub 2019 Jul 26.

Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030-3411, USA.

Background: Although mosaic variation has been known to cause disease for decades, high-throughput sequencing technologies with the analytical sensitivity to consistently detect variants at reduced allelic fractions have only recently emerged as routine clinical diagnostic tests. To date, few systematic analyses of mosaic variants detected by diagnostic exome sequencing for diverse clinical indications have been performed.

Methods: To investigate the frequency, type, allelic fraction, and phenotypic consequences of clinically relevant somatic mosaic single nucleotide variants (SNVs) and characteristics of the corresponding genes, we retrospectively queried reported mosaic variants from a cohort of ~ 12,000 samples submitted for clinical exome sequencing (ES) at Baylor Genetics.

Results: We found 120 mosaic variants involving 107 genes, including 80 mosaic SNVs in proband samples and 40 in parental/grandparental samples. Average mosaic alternate allele fraction (AAF) detected in autosomes and in X-linked disease genes in females was 18.2% compared with 34.8% in X-linked disease genes in males. Of these mosaic variants, 74 variants (61.7%) were classified as pathogenic or likely pathogenic and 46 (38.3%) as variants of uncertain significance. Mosaic variants occurred in disease genes associated with autosomal dominant (AD) or AD/autosomal recessive (AR) (67/120, 55.8%), X-linked (33/120, 27.5%), AD/somatic (10/120, 8.3%), and AR (8/120, 6.7%) inheritance. Of note, 1.7% (2/120) of variants were found in genes in which only somatic events have been described. Nine genes had recurrent mosaic events in unrelated individuals which accounted for 18.3% (22/120) of all detected mosaic variants in this study. The proband group was enriched for mosaicism affecting Ras signaling pathway genes.

Conclusions: In sum, an estimated 1.5% of all molecular diagnoses made in this cohort could be attributed to a mosaic variant detected in the proband, while parental mosaicism was identified in 0.3% of families analyzed. As ES design favors breadth over depth of coverage, this estimate of the prevalence of mosaic variants likely represents an underestimate of the total number of clinically relevant mosaic variants in our cohort.
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http://dx.doi.org/10.1186/s13073-019-0658-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6660700PMC
July 2019

Biallelic loss of function variants in PPP1R21 cause a neurodevelopmental syndrome with impaired endocytic function.

Hum Mutat 2019 03 25;40(3):267-280. Epub 2018 Dec 25.

Department of Genetic, Medicine and Development, University of Geneva Medical Faculty, Geneva, Switzerland.

Next-generation sequencing (NGS) has been instrumental in solving the genetic basis of rare inherited diseases, especially neurodevelopmental syndromes. However, functional workup is essential for precise phenotype definition and to understand the underlying disease mechanisms. Using whole exome (WES) and whole genome sequencing (WGS) in four independent families with hypotonia, neurodevelopmental delay, facial dysmorphism, loss of white matter, and thinning of the corpus callosum, we identified four previously unreported homozygous truncating PPP1R21 alleles: c.347delT p.(Ile116Lysfs*25), c.2170_2171insGGTA p.(Ile724Argfs*8), c.1607dupT p.(Leu536Phefs*7), c.2063delA p.(Lys688Serfs*26) and found that PPP1R21 was absent in fibroblasts of an affected individual, supporting the allele's loss of function effect. PPP1R21 function had not been studied except that a large scale affinity proteomics approach suggested an interaction with PIBF1 defective in Joubert syndrome. Our co-immunoprecipitation studies did not confirm this but in contrast defined the localization of PPP1R21 to the early endosome. Consistent with the subcellular expression pattern and the clinical phenotype exhibiting features of storage diseases, we found patient fibroblasts exhibited a delay in clearance of transferrin-488 while uptake was normal. In summary, we delineate a novel neurodevelopmental syndrome caused by biallelic PPP1R21 loss of function variants, and suggest a role of PPP1R21 within the endosomal sorting process or endosome maturation pathway.
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http://dx.doi.org/10.1002/humu.23694DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370506PMC
March 2019

De Novo Missense Variants in TRAF7 Cause Developmental Delay, Congenital Anomalies, and Dysmorphic Features.

Am J Hum Genet 2018 07 28;103(1):154-162. Epub 2018 Jun 28.

Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Baylor Genetics, Houston, TX 77021, USA.

TRAF7 is a multi-functional protein involved in diverse signaling pathways and cellular processes. The phenotypic consequence of germline TRAF7 variants remains unclear. Here we report missense variants in TRAF7 in seven unrelated individuals referred for clinical exome sequencing. The seven individuals share substantial phenotypic overlap, with developmental delay, congenital heart defects, limb and digital anomalies, and dysmorphic features emerging as key unifying features. The identified variants are de novo in six individuals and comprise four distinct missense changes, including a c.1964G>A (p.Arg655Gln) variant that is recurrent in four individuals. These variants affect evolutionarily conserved amino acids and are located in key functional domains. Gene-specific mutation rate analysis showed that the occurrence of the de novo variants in TRAF7 (p = 2.6 × 10) and the recurrent de novo c.1964G>A (p.Arg655Gln) variant (p = 1.9 × 10) in our exome cohort was unlikely to have occurred by chance. In vitro analyses of the observed TRAF7 mutations showed reduced ERK1/2 phosphorylation. Our findings suggest that missense mutations in TRAF7 are associated with a multisystem disorder and provide evidence of a role for TRAF7 in human development.
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http://dx.doi.org/10.1016/j.ajhg.2018.06.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6035372PMC
July 2018

Use of Exome Sequencing for Infants in Intensive Care Units: Ascertainment of Severe Single-Gene Disorders and Effect on Medical Management.

JAMA Pediatr 2017 12 4;171(12):e173438. Epub 2017 Dec 4.

Department of Pediatrics, Genetics Division, University of Tennessee Health Science Center, Memphis.

Importance: While congenital malformations and genetic diseases are a leading cause of early infant death, to our knowledge, the contribution of single-gene disorders in this group is undetermined.

Objective: To determine the diagnostic yield and use of clinical exome sequencing in critically ill infants.

Design, Setting, And Participants: Clinical exome sequencing was performed for 278 unrelated infants within the first 100 days of life who were admitted to Texas Children's Hospital in Houston, Texas, during a 5-year period between December 2011 and January 2017. Exome sequencing types included proband exome, trio exome, and critical trio exome, a rapid genomic assay for seriously ill infants.

Main Outcomes And Measures: Indications for testing, diagnostic yield of clinical exome sequencing, turnaround time, molecular findings, patient age at diagnosis, and effect on medical management among a group of critically ill infants who were suspected to have genetic disorders.

Results: The mean (SEM) age for infants participating in the study was 28.5 (1.7) days; of these, the mean (SEM) age was 29.0 (2.2) days for infants undergoing proband exome sequencing, 31.5 (3.9) days for trio exome, and 22.7 (3.9) days for critical trio exome. Clinical indications for exome sequencing included a range of medical concerns. Overall, a molecular diagnosis was achieved in 102 infants (36.7%) by clinical exome sequencing, with relatively low yield for cardiovascular abnormalities. The diagnosis affected medical management for 53 infants (52.0%) and had a substantial effect on informed redirection of care, initiation of new subspecialist care, medication/dietary modifications, and furthering life-saving procedures in select patients. Critical trio exome sequencing revealed a molecular diagnosis in 32 of 63 infants (50.8%) at a mean (SEM) of 33.1 (5.6) days of life with a mean (SEM) turnaround time of 13.0 (0.4) days. Clinical care was altered by the diagnosis in 23 of 32 patients (71.9%). The diagnostic yield, patient age at diagnosis, and medical effect in the group that underwent critical trio exome sequencing were significantly different compared with the group who underwent regular exome testing. For deceased infants (n = 81), genetic disorders were molecularly diagnosed in 39 (48.1%) by exome sequencing, with implications for recurrence risk counseling.

Conclusions And Relevance: Exome sequencing is a powerful tool for the diagnostic evaluation of critically ill infants with suspected monogenic disorders in the neonatal and pediatric intensive care units and its use has a notable effect on clinical decision making.
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http://dx.doi.org/10.1001/jamapediatrics.2017.3438DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6359927PMC
December 2017

Biallelic Variants in OTUD6B Cause an Intellectual Disability Syndrome Associated with Seizures and Dysmorphic Features.

Am J Hum Genet 2017 Apr 23;100(4):676-688. Epub 2017 Mar 23.

Laboratory for Pediatric Brain Disease, Howard Hughes Medical Institute, Department of Neurosciences, University of California, San Diego, CA 92093, USA.

Ubiquitination is a posttranslational modification that regulates many cellular processes including protein degradation, intracellular trafficking, cell signaling, and protein-protein interactions. Deubiquitinating enzymes (DUBs), which reverse the process of ubiquitination, are important regulators of the ubiquitin system. OTUD6B encodes a member of the ovarian tumor domain (OTU)-containing subfamily of deubiquitinating enzymes. Herein, we report biallelic pathogenic variants in OTUD6B in 12 individuals from 6 independent families with an intellectual disability syndrome associated with seizures and dysmorphic features. In subjects with predicted loss-of-function alleles, additional features include global developmental delay, microcephaly, absent speech, hypotonia, growth retardation with prenatal onset, feeding difficulties, structural brain abnormalities, congenital malformations including congenital heart disease, and musculoskeletal features. Homozygous Otud6b knockout mice were subviable, smaller in size, and had congenital heart defects, consistent with the severity of loss-of-function variants in humans. Analysis of peripheral blood mononuclear cells from an affected subject showed reduced incorporation of 19S subunits into 26S proteasomes, decreased chymotrypsin-like activity, and accumulation of ubiquitin-protein conjugates. Our findings suggest a role for OTUD6B in proteasome function, establish that defective OTUD6B function underlies a multisystemic human disorder, and provide additional evidence for the emerging relationship between the ubiquitin system and human disease.
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http://dx.doi.org/10.1016/j.ajhg.2017.03.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5384096PMC
April 2017

De Novo Truncating Variants in SON Cause Intellectual Disability, Congenital Malformations, and Failure to Thrive.

Am J Hum Genet 2016 09 18;99(3):720-727. Epub 2016 Aug 18.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Baylor Miraca Genetics Laboratories, Houston, TX 77021, USA. Electronic address:

SON is a key component of the spliceosomal complex and a critical mediator of constitutive and alternative splicing. Additionally, SON has been shown to influence cell-cycle progression, genomic integrity, and maintenance of pluripotency in stem cell populations. The clear functional relevance of SON in coordinating essential cellular processes and its presence in diverse human tissues suggests that intact SON might be crucial for normal growth and development. However, the phenotypic effects of deleterious germline variants in SON have not been clearly defined. Herein, we describe seven unrelated individuals with de novo variants in SON and propose that deleterious variants in SON are associated with a severe multisystem disorder characterized by developmental delay, persistent feeding difficulties, and congenital malformations, including brain anomalies.
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http://dx.doi.org/10.1016/j.ajhg.2016.06.035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5011061PMC
September 2016

Postnatal outcomes of prenatally diagnosed 45,X/46,XX.

Am J Med Genet A 2016 May 20;170A(5):1196-201. Epub 2016 Jan 20.

Division of Medical Genetics, University of Washington, Seattle, Washington.

High quality information is critical for informed decision-making in pregnancy following a prenatal diagnosis of sex chromosome aneuploidy. The goal of this study was to define the spectrum of outcomes in patients with prenatally diagnosed 45,X/46,XX mosaic Turner syndrome in order to provide a better basis for genetic counseling at the time of intrauterine diagnosis. Phenotype data for twenty-five patients with prenatally diagnosed 45,X/46,XX mosaicism were collected by retrospective chart review and, when possible, semi-structured telephone interview. Existing data from a cohort of 58 patients with postnatally diagnosed 45,X/46,XX mosaicism were used for comparison. Relative to those diagnosed postnatally, prenatal patients were more likely to have normal growth and normal secondary sexual development, less likely to manifest distinctive Turner syndrome features such as nuchal webbing and edema, and had significantly fewer renal defects. These differences underscore the need for a nuanced approach to prenatal counseling in cases of 45,X/46,XX mosaicism.
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http://dx.doi.org/10.1002/ajmg.a.37551DOI Listing
May 2016

Actionable exomic incidental findings in 6503 participants: challenges of variant classification.

Genome Res 2015 Mar 30;25(3):305-15. Epub 2015 Jan 30.

Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA;

Recommendations for laboratories to report incidental findings from genomic tests have stimulated interest in such results. In order to investigate the criteria and processes for assigning the pathogenicity of specific variants and to estimate the frequency of such incidental findings in patients of European and African ancestry, we classified potentially actionable pathogenic single-nucleotide variants (SNVs) in all 4300 European- and 2203 African-ancestry participants sequenced by the NHLBI Exome Sequencing Project (ESP). We considered 112 gene-disease pairs selected by an expert panel as associated with medically actionable genetic disorders that may be undiagnosed in adults. The resulting classifications were compared to classifications from other clinical and research genetic testing laboratories, as well as with in silico pathogenicity scores. Among European-ancestry participants, 30 of 4300 (0.7%) had a pathogenic SNV and six (0.1%) had a disruptive variant that was expected to be pathogenic, whereas 52 (1.2%) had likely pathogenic SNVs. For African-ancestry participants, six of 2203 (0.3%) had a pathogenic SNV and six (0.3%) had an expected pathogenic disruptive variant, whereas 13 (0.6%) had likely pathogenic SNVs. Genomic Evolutionary Rate Profiling mammalian conservation score and the Combined Annotation Dependent Depletion summary score of conservation, substitution, regulation, and other evidence were compared across pathogenicity assignments and appear to have utility in variant classification. This work provides a refined estimate of the burden of adult onset, medically actionable incidental findings expected from exome sequencing, highlights challenges in variant classification, and demonstrates the need for a better curated variant interpretation knowledge base.
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http://dx.doi.org/10.1101/gr.183483.114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4352885PMC
March 2015

Five children with deletions of 1p34.3 encompassing AGO1 and AGO3.

Eur J Hum Genet 2015 Jun 1;23(6):761-5. Epub 2014 Oct 1.

Medical Genetics Unit, Hospital Santa Maria della Misericordia, University of Perugia, Perugia, Italy.

Small RNAs (miRNA, siRNA, and piRNA) regulate gene expression through targeted destruction or translational repression of specific messenger RNA in a fundamental biological process called RNA interference (RNAi). The Argonaute proteins, which derive from a highly conserved family of genes found in almost all eukaryotes, are critical mediators of this process. Four AGO genes are present in humans, three of which (AGO 1, 3, and 4) reside in a cluster on chromosome 1p35p34. The effects of germline AGO variants or dosage alterations in humans are not known, however, prior studies have implicated dysregulation of the RNAi mechanism in the pathogenesis of several neurodevelopmental disorders. We describe five patients with hypotonia, poor feeding, and developmental delay who were found to have microdeletions of chromosomal region 1p34.3 encompassing the AGO1 and AGO3 genes. We postulate that haploinsufficiency of AGO1 and AGO3 leading to impaired RNAi may be responsible for the neurocognitive deficits present in these patients. However, additional studies with rigorous phenotypic characterization of larger cohorts of affected individuals and systematic investigation of the underlying molecular defects will be necessary to confirm this.
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http://dx.doi.org/10.1038/ejhg.2014.202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4795073PMC
June 2015

Periostin is a novel therapeutic target that predicts and regulates glioma malignancy.

Neuro Oncol 2015 Mar 19;17(3):372-82. Epub 2014 Aug 19.

Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington (A.M.M., S.A.M, S.N.E., C.A.P., R.G.O., J.R.S., R.C.R.); Department of Radiation Oncology, University of Washington School of Medicine, Seattle, Washington (A.D.T.); Division of Medical Genetics, Department of Internal Medicine, University of Washington School of Medicine, Seattle, Washington (M.J.T); Department of Bioengineering, University of Washington School of Medicine, Seattle, Washington (S.F., D.-H.K.); Department of Radiology, University of Washington School of Medicine, Seattle, Washington (K.R.T.-F.); Institute for Stem Cell and Regenerative Medicine, University of Washington School of Medicine, Seattle, Washington (A.M.M., S.A.M., S.F., D.-H.K., R.C.R.); Sage Bionetworks, Seattle, Washington (A.D.T.); Neuropathology Service, Department of Pathology, Stanford University School of Medicine, Stanford, California (D.E.B.); Laboratory of Immunology, IRCCS San Martino-IST Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy (B.C.); Case Western Reserve School of Medicine, Cleveland, Ohio (Y.K.); Neuroscience Associates, Boise, Idaho (T.C.M.).

Background: Periostin is a secreted matricellular protein critical for epithelial-mesenchymal transition and carcinoma metastasis. In glioblastoma, it is highly upregulated compared with normal brain, and existing reports indicate potential prognostic and functional importance in glioma. However, the clinical implications of periostin expression and function related to its therapeutic potential have not been fully explored.

Methods: Periostin expression levels and patterns were examined in human glioma cells and tissues by quantitative real-time PCR and immunohistochemistry and correlated with glioma grade, type, recurrence, and survival. Functional assays determined the impact of altering periostin expression and function on cell invasion, migration, adhesion, and glioma stem cell activity and tumorigenicity. The prognostic and functional relevance of periostin and its associated genes were analyzed using the TCGA and REMBRANDT databases and paired recurrent glioma samples.

Results: Periostin expression levels correlated directly with tumor grade and recurrence, and inversely with survival, in all grades of adult human glioma. Stromal deposition of periostin was detected only in grade IV gliomas. Secreted periostin promoted glioma cell invasion and adhesion, and periostin knockdown markedly impaired survival of xenografted glioma stem cells. Interactions with αvβ3 and αvβ5 integrins promoted adhesion and migration, and periostin abrogated cytotoxicity of the αvβ3/β5 specific inhibitor cilengitide. Periostin-associated gene signatures, predominated by matrix and secreted proteins, corresponded to patient prognosis and functional motifs related to increased malignancy.

Conclusion: Periostin is a robust marker of glioma malignancy and potential tumor recurrence. Abrogation of glioma stem cell tumorigenicity after periostin inhibition provides support for exploring the therapeutic impact of targeting periostin.
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http://dx.doi.org/10.1093/neuonc/nou161DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4483094PMC
March 2015

Actionable, pathogenic incidental findings in 1,000 participants' exomes.

Am J Hum Genet 2013 Oct 19;93(4):631-40. Epub 2013 Sep 19.

Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA; Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA 98195, USA; Department of Laboratory Medicine, University of Washington, Seattle, WA 98195, USA.

The incorporation of genomics into medicine is stimulating interest on the return of incidental findings (IFs) from exome and genome sequencing. However, no large-scale study has yet estimated the number of expected actionable findings per individual; therefore, we classified actionable pathogenic single-nucleotide variants in 500 European- and 500 African-descent participants randomly selected from the National Heart, Lung, and Blood Institute Exome Sequencing Project. The 1,000 individuals were screened for variants in 114 genes selected by an expert panel for their association with medically actionable genetic conditions possibly undiagnosed in adults. Among the 1,000 participants, 585 instances of 239 unique variants were identified as disease causing in the Human Gene Mutation Database (HGMD). The primary literature supporting the variants' pathogenicity was reviewed. Of the identified IFs, only 16 unique autosomal-dominant variants in 17 individuals were assessed to be pathogenic or likely pathogenic, and one participant had two pathogenic variants for an autosomal-recessive disease. Furthermore, one pathogenic and four likely pathogenic variants not listed as disease causing in HGMD were identified. These data can provide an estimate of the frequency (∼3.4% for European descent and ∼1.2% for African descent) of the high-penetrance actionable pathogenic or likely pathogenic variants in adults. The 23 participants with pathogenic or likely pathogenic variants were disproportionately of European (17) versus African (6) descent. The process of classifying these variants underscores the need for a more comprehensive and diverse centralized resource to provide curated information on pathogenicity for clinical use to minimize health disparities in genomic medicine.
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http://dx.doi.org/10.1016/j.ajhg.2013.08.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3791261PMC
October 2013

Swe1Wee1-dependent tyrosine phosphorylation of Hsp90 regulates distinct facets of chaperone function.

Mol Cell 2010 Feb;37(3):333-43

Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.

Saccharomyces WEE1 (Swe1), the only "true" tyrosine kinase in budding yeast, is an Hsp90 client protein. Here we show that Swe1(Wee1) phosphorylates a conserved tyrosine residue (Y24 in yeast Hsp90 and Y38 in human Hsp90alpha) in the N domain of Hsp90. Phosphorylation is cell-cycle associated and modulates the ability of Hsp90 to chaperone a selected clientele, including v-Src and several other kinases. Nonphosphorylatable mutants have normal ATPase activity, support yeast viability, and productively chaperone the Hsp90 client glucocorticoid receptor. Deletion of SWE1 in yeast increases Hsp90 binding to its inhibitor geldanamycin, and pharmacologic inhibition/silencing of Wee1 sensitizes cancer cells to Hsp90 inhibitor-induced apoptosis. These findings demonstrate that Hsp90 chaperoning of distinct client proteins is differentially regulated by specific posttranslational modification of a unique subcellular pool of the chaperone, and they provide a strategy to increase the cellular potency of Hsp90 inhibitors.
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http://dx.doi.org/10.1016/j.molcel.2010.01.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2824606PMC
February 2010