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1.  Cas Adaptor Proteins Organize the Retinal Ganglion Cell Layer Downstream of Integrin Signaling 
Neuron  2014;81(4):779-786.
Stratification of retinal neuronal cell bodies and lamination of their processes provide a scaffold upon which neural circuits can be built. However, the molecular mechanisms that direct retinal ganglion cells (RGCs) to resolve into a single-cell retinal ganglion cell layer (GCL) are not well understood. The extracellular matrix protein laminin conveys spatial information that instructs the migration, process outgrowth, and reorganization of GCL cells. Here, we show that the β1-Integrin laminin receptor is required for RGC positioning and reorganization into a single-cell GCL layer. β1-Integrin signaling within migrating GCL cells requires Cas signaling-adaptor proteins, and in the absence of β1-Integrin or Cas function retinal neurons form ectopic cell clusters beyond the inner limiting membrane (ILM), phenocopying laminin mutants. These data reveal a novel and essential role for Cas adaptor proteins in β1-Integrin-mediated signaling events critical for the formation of the single-cell GCL in the mammalian retina.
PMCID: PMC3988023  PMID: 24559672
2.  Autoimmune neutropenia preceding Helicobacter pylori-negative MALT lymphoma with nodal dissemination 
Autoimmune neutropenia (AIN), resulting from granulocyte-specific autoantibodies, is much less frequent than other autoimmune hematologic disorders including autoimmune hemolytic anemia (AIHA) and immune thrombocytopenia (ITP). These autoimmune disorders may precede, synchronize, or follow collagen disorders, viral infections, and lymphoid neoplasms. Herein we present the first case of AIN in association with Helicobacter pylori-negative mucosa-associated lymphoid tissue (MALT) lymphoma with nodal dissemination. In our case, AIN, accompanied by ITP, occurred prior to the clinical manifestation of lymphoma. AIN and ITP were well managed afterwards, but they relapsed in accordance with the recurrence of lymphoma. The administration of prednisolone at 0.5 mg/kg daily alleviated the cytopenias within a week. In general, combination chemotherapy is performed for the treatment of lymphoma-associated autoimmune hematologic disorders and indeed seems to be effective. Our case indicates that corticosteroid monotherapy may be effective for lymphoma-associated AIN especially when AIN precedes the onset of lymphoma.
PMCID: PMC4203267  PMID: 25337296
MALT lymphoma; autoimmune neutropenia; immune thrombocytopenia; corticosteroid; combination chemotherapy
3.  A requirement for Nedd9 in luminal progenitor cells prior to mammary tumorigenesis in MMTV-HER2/ErbB2 mice 
Oncogene  2013;33(4):411-420.
Overexpression of the NEDD9/HEF1/Cas-L scaffolding protein is frequent, and drives invasion and metastasis in breast, head and neck, colorectal, melanoma, lung, and other types of cancer. We have examined the consequences of genetic ablation of Nedd9 in the MMTV-HER2/ERBB2/neu mouse mammary tumor model. Unexpectedly, we found that only a limited effect on metastasis in MMTV-neu;Nedd9−/− mice compared to MMTV-neu;Nedd9+/+ mice, but instead a dramatic reduction in tumor incidence (18% versus 80%), and a significantly increased latency until tumor appearance. Orthotopic reinjection and tail vein injection of cells arising from tumors, coupled with in vivo analysis, indicated tumors arising in MMTV-neu;Nedd9−/− mice had undergone mutational selection that overcame the initial requirement for Nedd9. To better understand the defects in early tumor growth, we compared mammary progenitor cell pools from MMTV-neu;Nedd9−/− versus MMTV-neu;Nedd9+/+ mice. The MMTV-neu;Nedd9−/− genotype selectively reduced both the number and colony-forming potential of mammary luminal epithelial progenitor cells, while not affecting basal epithelial progenitors. MMTV-neu;Nedd9−/−mammospheres had striking defects in morphology and cell polarity. All of these defects were seen predominantly in the context of the HER2/neu oncogene, and were not associated with randomization of the plane of mitotic division, but rather with depressed expression the cell attachment protein FAK, accompanied by increased sensitivity to small molecule inhibitors of FAK and SRC. Surprisingly, in spite of these significant differences, only minimal changes were observed in the gene expression profile of Nedd9−/− mice, indicating critical Nedd9-dependent differences in cell growth properties were mediated via post-transcriptional regulation of cell signaling. Coupled with emerging data indicating a role for NEDD9 in progenitor cell populations during the morphogenesis of other tissues, these results indicate a functional requirement for NEDD9 in the growth of mammary cancer progenitor cells.
PMCID: PMC3628996  PMID: 23318423
breast cancer; HER2; mammary precursor cells; drug resistance
4.  Dynamic Metabolic Changes during the First 3 Months after 90Y-Ibritumomab Tiuxetan Radioimmunotherapy 
The Scientific World Journal  2014;2014:368947.
Objective. To elucidate the time course of tumor metabolism during the first 3 months after 90Y-ibritumomab tiuxetan radioimmunotherapy (RIT) in patients with refractory malignant lymphoma. Materials and Methods. Seven patients with recurrent follicular lymphoma underwent FDG-PET imaging before and after 1-, 4-, and 12-week RIT with 90Y-ibritumomab tiuxetan. Tumor metabolic activity on FDG-PET scans was assessed as the maximum standard uptake value (SUVmax). Results. Decrease in metabolism was detected 1 week after RIT. In the most decreased lesion, SUVmax decreased to 20% of the baseline value during the first week. Most lesions continued to decrease for up to 4 weeks. Some lesions showed increased metabolism from 4 to 12 weeks, while the level of FDG accumulations at 12 weeks was still lower than the baseline. Conclusions. Tumor response to RIT could be observed as early as 1 week after the administration of RIT. After tumor activity decreases, the metabolism may increase at least between 4 and 12 weeks. It suggests that the metabolic changes should be carefully evaluated during this period.
PMCID: PMC4090517  PMID: 25050390
5.  Pulmonary mucormycosis with embolism: two autopsied cases of acute myeloid leukemia 
Mucormycosis is an increasingly important cause of morbidity and mortality for patients with hematological malignancies. The diagnosis of mucormycosis usually requires mycological evidence through tissue biopsy or autopsy because the signs and symptoms are nonspecific and there are currently no biomarkers to identify the disease. We herein present two autopsied cases of acute myeloid leukemia with prolonged neutropenia who developed invasive mucormycosis accompanied by pulmonary artery embolism. Our cases were featured by unexplained fever and rapidly progressive dyspnea. Computed tomography scan detected nodular lesions or nonspecific consolidations in the lungs. Cultures, cytological study, and serum fungal markers consistently gave negative results. Autopsy revealed embolism of the pulmonary artery which consisted of fibrin clots by filamentous fungi. Genomic DNA was extracted from the paraffin-embedded clots and was applied to polymerase chain reaction amplification, leading to the diagnosis of infection by Rhizopus microsporus. We should carefully search for life-threatening pulmonary embolism when patients with hematological malignancies develop pulmonary mucormycosis.
PMCID: PMC4097268  PMID: 25031775
Rhizopus microsporus; mucormycosis; pulmonary embolism; acute myeloid leukemia; neutropenia
6.  Esophageal intramucosal hematoma after peripheral blood stem cell transplantation: case report and review of literature 
Esophageal complications occur after hematopoietic stem cell transplantation (HSCT). There are, however, only limited reports on the etiology or management of esophageal complications. Here, we report the occurrence of intramucosal hematoma presenting continuous esophageal hemorrhage in a 34 year-old man following the second peripheral blood stem cell transplantation for acute myeloid leukemia. His hematemesis started 2 months after HSCT and was repeated in supportive care. On day 156, he underwent total esophagectomy as a result of uncontrollable massive hematemesis. Histopathological testings of the resected esophagus confirmed intramucosal hematoma as a cause of hematemesis. This case highlights intramucosal hematoma as one of the important etiologies of esophageal complications following HSCT.
PMCID: PMC4069927  PMID: 24966988
Esophageal hemorrhage; intramucosal hematoma; esophagectomy; hematopoietic stem cell transplantation
7.  Positive feedback between NF-κB and TNF-α promotes leukemia-initiating cell capacity 
Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy that originates from leukemia-initiating cells (LICs). The identification of common mechanisms underlying LIC development will be important in establishing broadly effective therapeutics for AML. Constitutive NF-κB pathway activation has been reported in different types of AML; however, the mechanism of NF-κB activation and its importance in leukemia progression are poorly understood. Here, we analyzed myeloid leukemia mouse models to assess NF-κB activity in AML LICs. We found that LICs, but not normal hematopoietic stem cells or non-LIC fractions within leukemia cells, exhibited constitutive NF-κB activity. This activity was maintained through autocrine TNF-α secretion, which formed an NF-κB/TNF-α positive feedback loop. LICs had increased levels of active proteasome machinery, which promoted the degradation of IκBα and further supported NF-κB activity. Pharmacological inhibition of the proteasome complex markedly suppressed leukemia progression in vivo. Conversely, enhanced activation of NF-κB signaling expanded LIC frequency within leukemia cell populations. We also demonstrated a strong correlation between NF-κB activity and TNF-α secretion in human AML samples. Our findings indicate that NF-κB/TNF-α signaling in LICs contributes to leukemia progression and provide a widely applicable approach for targeting LICs.
PMCID: PMC3904603  PMID: 24382349
8.  HIV-associated Burkitt lymphoma in a Japanese patient with early submandibular swelling 
BMC Research Notes  2013;6:557.
Patients infected with the human immunodeficiency virus (HIV) are at risk of developing malignancies and have an increased susceptibility to infection. HIV-associated Burkitt lymphoma (BL) is relatively rare in developed countries, but remains prevalent in developing counties and is sometimes compounded by the fact that patients may be unaware that they are HIV-positive.
Case presentation
A 37-year-old Japanese man was referred to our department for diagnosis and management of submandibular swelling. He was unaware that he was HIV-positive at the initial visit. Here, we describe our diagnostic approach, in which we used hematological and immunological investigations, biopsy, fluorescence-activated cell sorting and fluorescence in situ hybridization to confirm the diagnosis of HIV-associated BL. The patient has no risk factors for HIV infection, and the source of infection remains unclear.
In this case, submandibular swelling was the first clinical sign of pathology and the patient’s HIV-positive status only became evident later. It is highly likely that BL was triggered by HIV infection.
PMCID: PMC3877969  PMID: 24370065
Burkitt lymphoma; HIV; Submandibular swelling
9.  Transformation of follicular lymphoma in the retroperitoneal muscles demonstrated by CT-guided needle biopsy of FDG-avid lesions; case series 
We herein report two cases of relapsed follicular lymphoma (FL) with transformation in the retroperitoneal muscles. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) combined with computed tomography (CT) showed high uptakes in the retroperitoneal muscles. We considered excisional biopsy at first, since it is definitely the most reliable means to obtain histological diagnosis. However, excisional biopsy of the retroperitoneal muscles is challenging for anatomical reasons. Moreover, our patients were kept under poor performance status. Thus, CT-guided percutaneous needle biopsy of FDG-avid retroperitoneal muscles was performed. Histopathological examination of the biopsied specimens demonstrated proliferation of transformed large B cells in both cases. Sheets of large B cells were also recorded in one case. CT-guided needle biopsy is less prioritized than excisional biopsy because of limited information on tissue architecture and increasingly complicated WHO classification. Our series indicate that image-guided needle biopsy of FDG-avid lesions is sufficient for the diagnosis of transformation. Higher priority should be given to this method in the setting of transformed aggressive lymphoma.
PMCID: PMC3885497  PMID: 24427363
Follicular lymphoma; transformation; retroperitoneum; FDG-avid; CT-guided needle biopsy
11.  Eleven secondary cancers after hematopoietic stem cell transplantation using a total body irradiation-based regimen in 370 consecutive pediatric and adult patients 
SpringerPlus  2013;2:424.
About the bone marrow transplantation that high dose chemotherapy and total-body irradiation (TBI) are used for as conditioning regimen, a late toxicity may become the problem in the long-term survival patient. One of the toxicities which has been implied to be associated with TBI is secondary cacinogenesis. Between June 1995 and December 2010, 370 patients who were undergoing allogeneic hematopoietic stem cell transplantation using a TBI-based regimen at our department, were the subjects of this study. Eleven secondary cancers occurred in 10 patients. The median time from transplantation to diagnosis of a secondary cancer was 6.8 years. In this analysis, the cumulative incidence rate of secondary cancer at 5 and 10 years was 2.15% and 6.46%, respectively after TBI in our institution.
PMCID: PMC3769541  PMID: 24040584
Total body irradiation; Secondary cancer; Bone marrow transplantation
12.  Transcription factor RUNX1 promotes survival of acute myeloid leukemia cells 
The Journal of Clinical Investigation  2013;123(9):3876-3888.
RUNX1 is generally considered a tumor suppressor in myeloid neoplasms. Inactivating RUNX1 mutations have frequently been found in patients with myelodysplastic syndrome (MDS) and cytogenetically normal acute myeloid leukemia (AML). However, no somatic RUNX1 alteration was found in AMLs with leukemogenic fusion proteins, such as core-binding factor (CBF) leukemia and MLL fusion leukemia, raising the possibility that RUNX1 could actually promote the growth of these leukemia cells. Using normal human cord blood cells and those expressing leukemogenic fusion proteins, we discovered a dual role of RUNX1 in myeloid leukemogenesis. RUNX1 overexpression inhibited the growth of normal cord blood cells by inducing myeloid differentiation, whereas a certain level of RUNX1 activity was required for the growth of AML1-ETO and MLL-AF9 cells. Using a mouse genetic model, we also showed that the combined loss of Runx1/Cbfb inhibited leukemia development induced by MLL-AF9. RUNX2 could compensate for the loss of RUNX1. The survival effect of RUNX1 was mediated by BCL2 in MLL fusion leukemia. Our study unveiled an unexpected prosurvival role for RUNX1 in myeloid leukemogenesis. Inhibiting RUNX1 activity rather than enhancing it could be a promising therapeutic strategy for AMLs with leukemogenic fusion proteins.
PMCID: PMC3754260  PMID: 23979164
13.  Successful treatment with recombinant thrombomodulin for B-cell lymphoma-associated hemophagocytic syndrome complicated by disseminated intravascular coagulation 
We report here a 47-year-old male with the diagnosis of high-grade B-cell lymphoma and hemophagocytosis accompanying disseminated intravascular coagulation (DIC). Lymphoma-associated hemophagocytic syndrome (LAHS) is a life-threatening disorder, and LAHS secondary to B-cell lymphoma is relatively rare compared to that secondary to T- or NK/T-cell lymphoma in Western countries. T- or NK/T-cell LAHS is sometimes combined with DIC, which makes patients’ outcomes even worse, but few reports of B-cell LAHS accompanying DIC has been published so far. We successfully treated a patient with this condition with recombinant thrombomodulin (rTM), a novel agent for DIC. We believe that rTM is a therapeutic option in cases with B-cell LAHS accompanying DIC.
PMCID: PMC3657377  PMID: 23696942
B-cell lymphoma; lymphoma-associated hemophagocytic syndrome; disseminated intravascular coagulation; recombinant thrombomodulin
14.  Acute myeloid leukemia with cryptic CBFB-MYH11 type D 
A 77 year-old female was found with FAB M4Eo acute myeloid leukemia. Although CBFB-MYH11 mRNA was detected in RT-PCR, the conventional cytogenetic analysis failed to reveal inv(16). Fluorescence in situ hybridization (FISH) and the sequence analysis revealed a fusion between the exon 5 of CBFB and the exon 8 of MYH11, resulting in a minor variant fusion product previously reported as type D. In order to detect the cryptic inv(16) type D, both FISH and RT-PCR are required, and furthermore, the primers for the sequence analysis needs to be selected for the proper diagnosis.
PMCID: PMC3515980  PMID: 23236551
Acute myeloid leukemia; inversion 16; CBFB-MYH11; RT-PCR; fluorescence in situ hybridization
15.  Evi1 is essential for hematopoietic stem cell self-renewal, and its expression marks hematopoietic cells with long-term multilineage repopulating activity 
The Journal of Experimental Medicine  2011;208(12):2403-2416.
A new mouse in which an IRES-GFP cassette is knocked-in to the Evi1 locus reveals that HSC long-term multilineage repopulating activity specifically segregates with expression of the Evi1 transcription factor.
Ecotropic viral integration site 1 (Evi1), a transcription factor of the SET/PR domain protein family, is essential for the maintenance of hematopoietic stem cells (HSCs) in mice and is overexpressed in several myeloid malignancies. Here, we generate reporter mice in which an internal ribosome entry site (IRES)-GFP cassette is knocked-in to the Evi1 locus. Using these mice, we find that Evi1 is predominantly expressed in long-term HSCs (LT-HSCs) in adult bone marrow, and in the hematopoietic stem/progenitor fraction in the aorta-gonad-mesonephros, placenta, and fetal liver of embryos. In both fetal and adult hematopoietic systems, Evi1 expression marks cells with long-term multilineage repopulating activity. When combined with conventional HSC surface markers, sorting according to Evi1 expression markedly enhances purification of cells with HSC activity. Evi1 heterozygosity leads to marked impairment of the self-renewal capacity of LT-HSCs, whereas overexpression of Evi1 suppresses differentiation and boosts self-renewal activity. Reintroduction of Evi1, but not Mds1-Evi1, rescues the HSC defects caused by Evi1 heterozygosity. Thus, in addition to documenting a specific relationship between Evi1 expression and HSC self-renewal activity, these findings highlight the utility of Evi1-IRES-GFP reporter mice for the identification and sorting of functional HSCs.
PMCID: PMC3256960  PMID: 22084405
16.  Evi1 forms a bridge between the epigenetic machinery and signaling pathways 
Oncotarget  2011;2(7):575-586.
Recent studies have demonstrated the significance of the leukemia oncogene Evi1 as the regulator of hematopoietic stem cells and marker of poor clinical outcomes in myeloid malignancies. Evi1-mediated leukemogenic activities include a wide array of functions such as the induction of epigenetic modifications, transcriptional control, and regulation of signaling pathways. We have recently succeeded in comprehensively elucidating the oncogenic function of Evi1 in a model of the polycomb-Evi1-PTEN/AKT/mTOR axis. These results may provide us with novel therapeutic approaches to conquer the poor prognosis associated with Evi1-activated leukemia or other solid tumors with high Evi1 expression. Here, we review the current understanding of the role of Evi1 in controlling the development of leukemia and highlight potential modalities for targeting factors involved in Evi1-regulated signaling.
PMCID: PMC3248179  PMID: 21795762
Evi1; Leukemia; Polycomb; PTEN; Rapamycin
17.  NEDD9 promotes oncogenic signaling in mammary tumor development 
Cancer research  2009;69(18):7198-7206.
In the past 3 years, altered expression of the HEF1/CAS-L/NEDD9 scaffolding protein has emerged as contributing to cancer metastasis in multiple cancer types. However, while some studies have identified elevated NEDD9 expression as pro-metastatic, other work has suggested a negative role in tumor progression. We here show that the Nedd9 null genetic background significantly limits mammary tumor initiation in the MMTV-polyoma virus middle T (PyVmT) genetic model. Action of Nedd9 is tumor cell intrinsic, with immune cell infiltration, stroma, and angiogenesis unaffected. The majority of the late-appearing mammary tumors of MMTV-PyVmT;Nedd9-/- mice are characterized by depressed activation of proteins including AKT, SRC, FAK, and ERK, emphasizing an important role of Nedd9 as a scaffolding protein for these pro-oncogenic proteins. Analysis of cells derived from primary Nedd9+/+ and Nedd9-/- tumors demonstrated persistently reduced FAK activation, attachment, and migration, consistent with a role for NEDD9 activation of FAK in promoting tumor aggressiveness. This study provides the first in vivo evidence of a role for NEDD9 in breast cancer progression, and suggests that Nedd9 expression may provide a biomarker for tumor aggressiveness.
PMCID: PMC2758619  PMID: 19738060
18.  Comparison of temporal changes in psychological distress after hematopoietic stem cell transplantation among the underlying diseases of Japanese adult patients 
Although hematopoietic stem cell transplantation (HSCT) can potentially cure some hematological malignancies, patients who undergo HSCT experience psychological distress. However, there have been few studies on the short-term influence of HSCT on psychological distress.
The subjects were 71 patients with hematological malignancies who underwent HSCT: 33 with acute leukemia, 19 with chronic leukemia, nine with myelodysplastic syndrome, and 10 with malignant lymphoma. Psychological distress was assessed prior to HSCT and on the seventh day after HSCT using the Profile of Mood States (POMS).
With regard to Anger-Hostility, the interaction of time (pre- and post-HSCT) and group (the four groups) was significant in male patients (p = 0.04), but not in female patients. With regard to the other subscales of POMS, there was no significant main effect or interaction in male or female patients.
It may be important to provide psychological support to patients throughout the period of HSCT in consideration of differences in mood changes associated with the underlying disease and patient sex in order to provide efficient psychiatric intervention for both better psychiatric and survival outcomes.
PMCID: PMC2603014  PMID: 19025589
19.  Prospective Comparison of the Diagnostic Potential of Real-Time PCR, Double-Sandwich Enzyme-Linked Immunosorbent Assay for Galactomannan, and a (1→3)-β-d-Glucan Test in Weekly Screening for Invasive Aspergillosis in Patients with Hematological Disorders 
Journal of Clinical Microbiology  2004;42(6):2733-2741.
The establishment of an optimal noninvasive method for diagnosing invasive aspergillosis (IA) is needed to improve the management of this life-threatening infection in patients with hematological disorders, and a number of noninvasive tests for IA that target different fungal components, including galactomannan, (1→3)-β-d-glucan (BDG), and Aspergillus DNA, have been developed. In this study, we prospectively evaluated the diagnostic potential of three noninvasive tests for IA that were used in a weekly screening strategy: the double-sandwich enzyme-linked immunosorbent assay (ELISA) for galactomannan (Platelia Aspergillus), a real-time PCR assay for Aspergillus DNA (GeniQ-Asper), and an assay for BDG (β-glucan Wako). We analyzed 149 consecutive treatment episodes in 96 patients with hematological disorders who were at high risk for IA and diagnosed 9 proven IA cases, 2 probable IA cases, and 13 possible invasive fugal infections. In a receiver-operating characteristic (ROC) analysis, the area under the ROC curve was greatest for ELISA, using two consecutive positive results (0.97; P = 0.036 for ELISA versus PCR, P = 0.055 for ELISA versus BDG). Based on the ROC curve, the cutoff for the ELISA could be reduced to an optical density index (O.D.I.) of 0.6. With the use of this cutoff for ELISA and cutoffs for PCR and BDG that give a comparable level of specificity, the sensitivity/specificity/positive predictive value/negative predictive value of the ELISA and the PCR and BDG tests were 1.00/0.93/0.55/1.00, 0.55/0.93/0.40/0.96, and 0.55/0.93/0.40/0.96, respectively. In conclusion, among these weekly screening tests for IA, the double-sandwich ELISA test was the most sensitive at predicting the diagnosis of IA in high-risk patients with hematological disorders, using a reduced cutoff of 0.6 O.D.I.
PMCID: PMC427860  PMID: 15184460
20.  Leukemia-Related Transcription Factor TEL Is Negatively Regulated through Extracellular Signal-Regulated Kinase-Induced Phosphorylation 
Molecular and Cellular Biology  2004;24(8):3227-3237.
TEL is an ETS family transcription factor that possesses multiple putative mitogen-activated protein kinase phosphorylation sites. We here describe the functional regulation of TEL via ERK pathways. Overexpressed TEL becomes phosphorylated in vivo by activated ERK. TEL is also directly phosphorylated in vitro by ERK. The inducible phosphorylation sites are Ser213 and Ser257. TEL binds to a common docking domain in ERK. In vivo ERK-dependent phosphorylation reduces trans-repressional and DNA-binding abilities of TEL for ETS-binding sites. A mutant carrying substituted glutamates on both Ser213 and Ser257 functionally mimics hyperphosphorylated TEL and also shows a dominant-negative effect on TEL-induced transcriptional suppression. Losing DNA-binding affinity through phosphorylation but heterodimerizing with unmodified TEL could be an underlying mechanism. Moreover, the glutamate mutant dominantly interferes with TEL-induced erythroid differentiation in MEL cells and growth suppression in NIH 3T3 cells. Finally, endogenous TEL is dephosphorylated in parallel with ERK inactivation in differentiating MEL cells and is phosphorylated through ERK activation in Ras-transformed NIH 3T3 cells. These data indicate that TEL is a constituent downstream of ERK in signal transduction systems and is physiologically regulated by ERK in molecular and biological features.
PMCID: PMC381595  PMID: 15060146
21.  The Corepressor mSin3A Regulates Phosphorylation-Induced Activation, Intranuclear Location, and Stability of AML1 
Molecular and Cellular Biology  2004;24(3):1033-1043.
The AML1 (RUNX1) gene, one of the most frequent targets of translocations associated with human leukemias, encodes a DNA-binding protein that plays pivotal roles in myeloid differentiation through transcriptional regulation of various genes. Previously, we reported that AML1 is phosphorylated on two serine residues with dependence on activation of extracellular signal-regulated kinase, which positively regulates the transcriptional activity of AML1. Here, we demonstrate that the interaction between AML1 and the corepressor mSin3A is regulated by phosphorylation of AML1 and that release of AML1 from mSin3A induced by phosphorylation activates its transcriptional activity. Furthermore, phosphorylation of AML1 regulates its intranuclear location and disrupts colocalization of AML1 with mSin3A in the nuclear matrix. PEBP2β/CBFβ, a heterodimeric partner of AML1, was shown to play a role in protecting AML1 from proteasome-mediated degradation. We show that mSin3A also protects AML1 from proteasome-mediated degradation and that phosphorylation-induced release of AML1 from mSin3A results in degradation of AML1 in a time-dependent manner. This study provides a novel regulatory mechanism for the function of transcription factors mediated by protein modification and interaction with cofactors.
PMCID: PMC321417  PMID: 14729951
22.  Binding of Delta1, Jagged1, and Jagged2 to Notch2 Rapidly Induces Cleavage, Nuclear Translocation, and Hyperphosphorylation of Notch2 
Molecular and Cellular Biology  2000;20(18):6913-6922.
Delta1, Jagged1, and Jagged2, commonly designated Delta/Serrate/LAG-2 (DSL) proteins, are known to be ligands for Notch1. However, it has been less understood whether they are ligands for Notch receptors other than Notch1. Meanwhile, ligand-induced cleavage and nuclear translocation of the Notch protein are considered to be fundamental for Notch signaling, yet direct observation of the behavior of the Notch molecule after ligand binding, including cleavage and nuclear translocation, has been lacking. In this report, we investigated these issues for Notch2. All of the three DSL proteins bound to endogenous Notch2 on the surface of BaF3 cells, although characteristics of Jagged2 for binding to Notch2 apparently differed from that of Delta1 and Jagged1. After binding, the three DSL proteins induced cleavage of the membrane-spanning subunit of Notch2 (Notch2TM), which occurred within 15 min. In a simultaneous time course, the cleaved fragment of Notch2TM was translocated into the nucleus. Interestingly, the cleaved Notch2 fragment was hyperphosphorylated also in a time-dependent manner. Finally, binding of DSL proteins to Notch2 also activated the transcription of reporter genes driven by the RBP-Jκ-responsive promoter. Together, these data indicate that all of these DSL proteins function as ligands for Notch2. Moreover, the findings of rapid cleavage, nuclear translocation, and phosphorylation of Notch2 after ligand binding facilitate the understanding of the Notch signaling.
PMCID: PMC88767  PMID: 10958687

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