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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
Cytokine. Author manuscript; available in PMC 2010 June 1.
Published in final edited form as:
PMCID: PMC2693279
NIHMSID: NIHMS100376

Lack of nuclear translocation of cytoplasmic domains of IL-2/IL-15 receptor subunits

Abstract

Some sensors of extracellular signaling molecules such as Notch and sterol response element binding protein (SREBP) receive ligand-induced intra-membrane proteolysis followed by nuclear translocation of their cytoplasmic domains to regulate gene expression programs in the nucleus. It has not been extensively examined whether ligand-induced intra-membrane proteolysis of type I cytokine receptors and nuclear translocation of cytoplasmic domains occur. Here, by using a sensitive reporter system, we examined this possibility for the interleukin-2 (IL-2) receptor (IL-2R) β-chain (IL-2Rβ) and the IL-15 receptor (IL-15R) α-chain (IL-15Rα). Flowcytometric analysis revealed that ligand stimulation does not induce nuclear translocation of their cytoplasmic domains. In addition, overexpression of the cytoplasmic domain of the common cytokine receptor γ-chain (γc) in an IL-2R-reconstituted Ba/F3-derived cell line did not affect any biological responses including cell survival, disproving potential roles of the cleaved cytoplasmic domain of γc as a signal transducer. Collectively, these results indicated that potential nuclear function of cleaved type I cytokine receptor subunits is not plausible.

Keywords: cytokine, regulated intra-membrane proteolysis, nuclear translocation, inducible translocation trap

1. Introduction

Some sensors of extracellular and intracellular signaling molecules receive ligand-induced intra-membrane proteolysis followed by nuclear translocation of their cytoplasmic domains to regulate gene expression programs in the nucleus [1]. For example, binding of Delta-like ligands to Notch induces a proteolytic cascade, ultimately resulting in release of Notch intracellular domain (NICD). NICD enters into the nucleus and acts as a component of transcriptional activator complex. Another example is SREBP, which is released by the proteolysis of a membrane protein precursor within the membrane in response to changes in internal sterol concentrations and regulates gene expression in the nucleus [2,3].

Accumulating evidence suggests critical importance of the Jak/Stat pathway in signal transduction from type I and type II cytokine receptors [4,5]. On the other hand, other signaling pathways are also activated upon cytokine binding [6], and it is possible that these receptors may also use different modes of signal transduction. In this regard, it has not been extensively examined whether ligand-induced intra-membrane proteolysis of type I cytokine receptors and nuclear translocation of cytoplasmic domains occur.

Here, by using a sensitive reporter system, we examined this possibility for IL-2Rβ and IL-15Rα. Flowcytometric analysis revealed that ligand stimulation does not induce nuclear translocation of their cytoplasmic domains. In addition, overexpression of the cytoplasmic domain of γc in an IL-2R-reconstituted Ba/F3-derived cell line did not affect any biological responses including cell survival, disproving potential roles of the cleaved cytoplasmic domain of γc as a signal transducer. Collectively, these results indicated that potential nuclear function of cleaved type I cytokine receptor subunits is not plausible.

2. Materials and Methods

2.1. Plasmids construction

For constuction of Notch1-LGV/pMXs expressing the fusion protein of human Notch1 and LGV, the Hind III - Sfi I fragment (7.3 kbp) and the Sfi I - BspE I fragment (371 bp) of the pcDNA3-1-hNotch1-FLAG plasmid [7] were cloned into the pMXs vector together with Xmn I- and Sal 1-digested LGV and a double-strand oligonulceotide consisting of 5′-GATCCGGAGGCC TTCAA -3′ and 5′-TTGAAGGCCTCCG -3′.

LGV (NLS+)/pMX is a retroviral construct expressing the LGV (NLS+) protein consisting of DNA-binding domain (DB) and the dimerization domain of LexA, GFP and VP16 transactivation domain (TA). It was shown that the dimerization domain of LexA contains a criptic nuclear localization signal (NLS) [8].

For construction of IL-2Rβ-LGV/pMX expressing the fusion protein of mouse IL-2Rβ and the LGV protein consisting of LexA DB, GFP, and VP16 TA, the carboxyl (C)-terminal region of mouse IL-2Rβ cDNA was amplified by PCR using mouse IL-2Rβ WT/pBS [9] as template and 5′-aggctgcccgagggatctccccac-3′ and 5′-aaatcccgggattaggtggactgaatcttgggc-3′ as primers. The PCR product was subcloned into the pCR2.1 vector (Invitrogen) and verified by sequencing. The cDNA encoding the LGV protein was digested from pLGV-N, which is a modified version of pLGV [10], with Xmn I and BamH I and inserted into Sma I- and BamH I-cleaved pCR2.1 plasmid containing the C-terminal region of mouse IL-2Rβ cDNA. The resultant plasmid was digested with BamH I, the ends were filled-in with T4 DNA polymerase (DNA Blunting kit, Takara), and subsequently digested with Apa I. The cDNA encoding the fusion protein of the C-terminal region of mouse IL-2Rβ and LGV was ligated into the pMX vector [11] together with the cDNA encoding the amino-terminal region of mouse IL-2Rβ derived from mIL-2Rβ WT/pBS. LGV does not contain any NLS.

For construction of IL-15Rα-LGV/pMX expressing the fusion protein of mouse IL-15Rα and LGV, mouse IL-15Rα cDNA [12] was amplified by PCR using 5′-actaaagcttgggtcactgctggggacaattggcc-3′ and 5′-caaacccggggctcctgtgtcttcatcctccttgct-3′ as primers. The PCR product was digested with EcoR I and subcloned into pBluescript SK (+) and verified by sequencing. The resultant plasmid was cleaved with BamH I and Sma I, and the Xmn I- and BamH I-digested LGV cDNA was inserted. The cDNA encoding a fusion protein of mouse IL-15Rα and LGV was inserted into pMX.

For construction of IL-2Rβ/pMX expressing mouse IL-2Rβ, IL-2Rβ cDNA was inserted into pMX.

For construction of HA-γc (cyto)/pEF expressing the HA-tagged cytoplasmic domain of human γc (HA-γc (cyto)), cDNA encoding a region of the cytoplasmic domain of γc cleaved from pIL-2Rγ2 [13] with Nsp I, which was blunted, and EcoR I was inserted into pEF-HA [14] digested with Xba I, which was filled in, and EcoR I, together with phosphorylated oligonucleotides generated by anealing 5′-ggccgcactggaacggacgatgccccg-3′ and 5′-aattcggggcatcgtccgttccagtgc-3′.

For construction of HA-γc (cyto)/pUHD10-3 expressing HA-γc (cyto) in a tetracycline-inducible manner, cDNA encoding a region of the cytoplasmic domain of γc cleaved from pIL-2Rγ2 with Nsp I, which was blunted, and EcoR I was inserted into pUHD10-3 [15] digested with Xba I, which was filled in, and EcoR I. The resultant plasmid was cleaved with EcoR I and inserted with the fragment encoding the HA-tag and a portion of the cytoplasmic domain of γc derived from EcoR I-digested HA-γc (cyto)/pEF.

2.2. Cell lines

BL2 is a Ba/F3-derived cell line containing the LexA-hCD2 reporter gene [10]. F7-rtTA3 is derived from F7, which is a Ba/F3-derived cell line expressing human IL-2Rβ, and expresses rtTA from the transfected pUHD172-1 plasmid [15].

2.3. Retroviral gene transduction

Retroviral gene transfer was performed as previously described [10].

2.4. Establishment of stable transformants

Establishment of stable transformants was done as previously described [10]. Briefly, 100 μg of pUHD172-1 or HA-γc (cyto)/pUHD10-3 was linearlized with Xho I or Pvu I, respectively, and transfected into 1 × 107 of F7 or F7-rtTA3 cells together with the linearlized puromycin- or hygromycin-resistant gene, respectively, by electroporation. Transfected cells were cultured in RPMI 1640 medium supplemented with 10% fetal calf serum (FCS) and 10% WEHI-3B-conditioned medium in the presence of puromycin (0.75 μg/ml) or hygromycin B (1 mg/ml).

2.5. Flowcytometry

Flowcytometric analysis of GFP and hCD2 expression was performed as previously described [10].

2.6. Immunoprecipitation and immunoblot analysis

Immunoprecipitation and immunoblot analysis were performed as described previously [16]. Antibodies (Abs) used for immunoblot analysis in this study are anti-IL-2Rβ (sc-672), anti-γc (sc-668). anti-Sp1 (sc-59), anti-Rho GDI (sc-360, Santa Cruz Biotechnology), anti-LexA (06-719), anti-RNA polymerase II (05-623, Upstate Biotechnology), anti-CD4 (Leu3a), and anti-HA (12CA5) Abs.

2.7. Northern blot analysis

Northern blot analysis of the cytoplasmic domain of human γc gene was performed as described previously [14,17,18].

2.8. Cell death assay

Cells were cultured in RPMI 1640 medium supplemented with 10% FCS and human IL-2 (10 ng/ml) in the absence or presence of doxycycline (DOX) (10 μg/ml) for 24 hr. Subsequently, cells were cultured in media that did not contain IL-2. Cell viability was examined by propidium iodide (PI) staining and flowcytometry.

3. Results and discussion

3.1. Detection of nuclear translocation of NICD by ITT

To address the issue of potential ligand-induced nuclear translocation of the cytoplasmic domains of type I cytokine receptors, we used a sensitive human CD2 (hCD2) reporter system of the inducible translocation trap (ITT) system [10]. This system consists of the LexA-hCD2 reporter gene composed of hCD2 with multiple LexA-binding sites and fusion proteins of cytokine receptor subunits and LGV, a fusion protein of LexA DB, GFP, and VP16 TA (Fig. 1A). If cytoplasmic domains of cytokine receptor subunits are cleaved upon ligand stimulation and translocate into the nucleus, LGV binds to the LexA-binding elements of the LexA-hCD2 reporter and induces expression of hCD2.

Figure 1
Detection of nuclear translocation of NICD by ITT. (A) Scheme of human Notch1 fused with LGV (Notch1-LGV). (B) Expression of Notch1-LGV. Notch1-LGV/pMXs was transduced into BL2 as described previously [10]. Expression of GFP was compared between GFP (−) ...

To examine whether this system can detect nuclear translocation of cytoplasmic domains of cell surface receptors, we generated a retroviral construct expressing the human Notch1 [7] fused with LGV (Notch1-LGV, Fig. 1A) and transduced into the BL2 cell line. BL2 is a Ba/F3-derived cell line containing the LexA-hCD2 reporter gene [10]. Expression of GFP was clearly detected by flowcytometry (Fig. 1B), showing the expression of the Notch1-LGV fusion protein. We treated transduced cells with EDTA, which depletes calcium and has been reported to activate Notch receptors [19]. In the absence of EDTA treatment, background expression of hCD2 was observed (Fig. 1C), suggesting spontaneous activation of Notch1 or activation by endogenous Notch ligand possibly expressed on Ba/F3-derived cell lines. EDTA treatment increased the percentages of hCD2high populations in a dose-dependent manner (Fig. 1C and D), indicating increase in the amounts of NICD in response to calcium depletion. These results showed that the ITT system is sensitive enough to detect nuclear translocation of cytoplasmic domains of cell surface receptors induced by intra-membrane cleavage.

3.2. Lack of IL-2-induced nuclear translocation of the cytoplasmic domain of IL-2Rβ

Next, we examined possible nuclear translocation of IL-2Rβ. IL-2Rβ is a shared subunit of IL-2R and IL-15R and a member of the type I cytokine receptor family [5]. LGV (NLS+)/pMX (positive control), a retroviral construct expressing LGV (NLS+), which constitutively resides in the nucleus and activates reporter expression, or IL-2Rβ-LGV/pMX, a retroviral construct expressing the fusion protein of mouse IL-2Rβ and the LGV protein (Fig. 2A), was transduced into BL2 cells. Transduced cells were cultured in the presence of IL-3 (1 ng/ml) or IL-2 (10 ng/ml) for two days, and GFP expression as well as hCD2 reporter expression was analyzed by flowcytometry. IL-2Rβ-LGV-transduced BL2 cells proliferated in response to IL-2 (data not shown), indicating that IL-2Rβ-LGV retains the ability to transmit proliferative singal. As shown in Fig. 2B, comparable expression levels of LGV (NLS+) and IL-2Rβ-LGV were observed. On GFP (+) BL2 cells expressing LGV (NLS+), hCD2 expression was readily detected (Fig. 2C and D). In contrast, no hCD2 reporter expression was detected on GFP (+) BL2 cells expressing IL-2Rβ-LGV cultured in the presence of IL-3 or IL-2 (Fig. 2C and D). This result showed that ligand-induced nuclear translocation of the cytoplasmic domain of IL-2Rβ does not occur.

Figure 2
Lack of IL-2-induced nuclear translocation of the cytoplasmic domain of IL-2Rβ. (A) IL-2R expression was reconstituted in BL2 cells by ectopic expression of IL-2Rβ-LGV. Potential cleavage and nuclear translocation of the cytoplasmic domain ...

To further confirm lack of IL-2-induced nuclear translocation of the cytoplasmic domain of IL-2R subunits, we performed immunoblot analysis of cytoplasmic domains of IL-2Rβ and γc. Ba/F3 cells expressing mouse IL-2Rβ were growth factor-starved for 4 hrs and stimulated with mouse IL-2 (10 ng/ml) for the indicated time intervals. Cytoplasmic and nuclear extracts were prepared and subjected to immunoblot analysis with anti-IL-2Rβ, anti-γc, anti-Sp1, or anti-Rho GDI Ab. As shown in Fig. 3, cytoplasmic domains of γc were not detected following IL-2 stimulation. There was one main band (55 kDa) in the anti-IL-2Rβ blot of the nuclear extracts (Fig. 3). At this stage, it is not clear whether this band is a cleaved cytoplasmic domain of IL-2Rβ or non-specific bands. However, intensity of this band did not change by IL-2 stimulation (Fig. 3), arguing against its functional roles in signal transduction. These data collectively confirmed lack of IL-2-induced nuclear translocation of the cytoplasmic domain of IL-2R subunits.

Figure 3
Lack of IL-2-induced nuclear translocation of the cytoplasmic domain of IL-2Rβ. Ba/F3 cells expressing mouse IL-2Rβ were growth factor-starved for 4 hrs and stimulated with mouse IL-2 (10 ng/ml) for the indicated time intervals. Cytoplasmic ...

3.3. Lack of IL-15-induced nuclear translocation of the cytoplasmic domain of IL-15Rα

Next, we examined possible nuclear translocation of IL-15Rα. IL-15Rα is the IL-15-specific subunit of IL-15R [20]. It does not belong to the type I cytokine receptor family but is structurally related to IL-2Rα [20]. LGV (NLS+)/pMX (positive control) or IL-15Rα-LGV/pMX, a retroviral construct expressing the fusion protein of mouse IL-15Rα and the LGV protein (Fig. 4A), was transduced into BL2 cells ectopically expressing mouse IL-2Rβ by transduction of IL-2Rβ/pMX. Transduced cells were cultured in the presence of IL-3 (1 ng/ml) or IL-15 (10 ng/ml) for two days, and GFP expression as well as hCD2 reporter expression was analyzed by flowcytometry. IL-15Rα-LGV-transduced BL2 cells expressing IL-2Rβ proliferated in response to IL-15 (data not shown), indicating that IL-15Rα-LGV retains the ability to transmit proliferative signal. As shown in Fig. 4B, comparable expression levels of LGV (NLS+) and IL-15Rα-LGV were observed. On GFP (+) cells expressing LGV (NLS+), hCD2 expression was readily detected. In contrast, marginal hCD2 reporter expression identical to that for GFP (−) population was detected on GFP (+) cells expressing IL-15Rα-LGV cultured in the presence of IL-3 or IL-15 (Fig. 4C and D). This result showed that ligand-induced nuclear translocation of the cytoplasmic domain of IL-15Rα does not occur.

Figure 4
Lack of IL-15-induced nuclear translocation of the cytoplasmic domain of IL-15Rα. (A) IL-15R expression was reconstituted in BL2 cells expressing mouse IL-2Rβ by transduction of IL-15Rα-LGV. Potential cleavage and nuclear translocation ...

To further confirm lack of IL-2-induced nuclear translocation of the cytoplasmic domain of IL-15R subunits, we performed immunoblot analysis of cytoplasmic domains of IL-2Rβ and γc. Ba/F3 cells expressing mouse IL-2Rβ and mouse IL-15Rα fused with LGV were growth factor-starved for 4 hrs and stimulated with human IL-15 (10 ng/ml) for the indicated time intervals. Cytoplasmic and nuclear extracts were prepared and subjected to immunoblot analysis with anti-LexA, anti-IL-2Rβ, anti-γc, anti-Sp1, or anti-Rho GDI Ab. As shown in Fig. 5, cytoplasmic domains of γc were not detected following IL-15 stimulation. There were one main band (55 kDa) and a faint band (43 kDa) in the anti-IL-2Rβ blot of the nuclear extracts (Fig. 5). At this stage, it is not clear whether these bands are cleaved cytoplasmic domains of IL-2Rβ or non-specific bands. However, intensities of these bands did not change by IL-15 stimulation, arguing against their functional roles in signal transduction. These data further confirmed the lack of IL-15-induced nuclear translocation of the cytoplasmic domain of IL-15R subunits.

Figure 5
Lack of IL-15-induced nuclear translocation of the cytoplasmic domain of IL-15Rα. Ba/F3 cells expressing mouse IL-2Rβ and mouse IL-15Rα fused with LGV were growth factor-starved for 4 hrs and stimulated with human IL-15 (10 ng/ml) ...

3.4. Lack of biological activities of the overexpressed cytoplasmic domain of γc

In Notch signaling, NICD functions as an active form and overexpression of NICD induces malignant transformation [21]. As a complementary approach to the above-mentioned reporter-dependent detection of nuclear translocation of cytoplasmic domains of cytokine receptors, we examined whether cytoplasmic domains of cytokine receptors function as active forms using γc as an example. The cytoplasmic domain of γc was fused with the HA-tag (HA-γc (cyto)) (Fig. 6A). Co-transfection assay showed that HA-γc (cyto) retains the ability to bind Jak3 (Fig. 6B). We established IL-2R-reconstituted F7-derived clones that express HA-γc (cyto) in a tetracycline-dependent manner (Fig. 6C). To examine biological effects of overexpression of HA-γc (cyto), cells cultured in the presence of IL-2 were growth factor-starved in the absence or presence of doxycycline (Dox), and their viability was examined by PI staining and flowcytometry. As shown in Fig. 6D, there was no difference in cell viability after IL-2-starvation between Dox (−) and Dox (+) cells. Cell proliferation was also not affected by Dox-induced expression of HA-γc (cyto) (data not shown). Thus, overexpression of HA-γc (cyto) did not show any biological effects tested.

Figure 6
Overexpression of the cytoplasmic domain of γc in an IL-2R-reconstituted Ba/F3-derived cell line did not affect cell viability after IL-2 withdrawal. (A) Scheme of HA-tagged cytoplasmic domain of human γc (HA-γc (cyto)). (B) Physical ...

3.5. No evidence of nuclear translocation of cytoplasmic domains of type I cytokine receptor subunits

Here, we examined possible nuclear translocation of type I cytokine receptor subunits and its potential significance in signal transduction. ITT-based reporter assay was sensitive enough to detect nuclear translocation of NICD induced by intra-membrane cleavage. Our results clearly showed that there is no nuclear translocation of IL-2Rβ and IL-15Rα in response to IL-2 and IL-15 stimulation, respectively. Another approach using overexpression of the cytoplasmic domain of γc did not show any indication of its biological activities. Thus, it is not likely that type I cytokine receptors use a similar signal transduction mechanism to that utilized by Notch and SREBP.

Acknowledgments

We thank Drs. T. Taniguchi and I. Aifantis for mouse IL-2Rβ cDNA and Ba/F3-derived cell lines and hNotch1 cDNA, respectively. We also thank Dr. H. Bujard for the tetracycline-inducible expression system. We also thank S. Saint Fleur for critical reading of the manuscript.

Footnotes

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References

1. Brivanlou AH, Darnell JE., Jr Signal transduction and the control of gene expression. Science. 2002;295:813–8. [PubMed]
2. Brown MS, Goldstein JL. The SREBP pathway: regulation of cholesterol metabolism by proteolysis of a membrane-bound transcription factor. Cell. 1997;89:331–40. [PubMed]
3. Brown MS, Goldstein JL. A proteolytic pathway that controls the cholesterol content of membranes, cells, and blood. Proc Natl Acad Sci USA. 1999;96:11041–8. [PubMed]
4. Levy DE, Darnell JE., Jr Stats: Transcriptional control and biological impact. Nat Rev Mol Cell Biol. 2002;3:651–62. [PubMed]
5. Leonard WJ. Type I Cytokines and Interferons and their receptors. In: Paul WE, editor. Fundamental Immunology. Lippincott Williams & Wilkins; Philadelphia, PA: 2003. pp. 701–47.
6. Taniguchi T. Cytokine signaling through nonreceptor protein tyrosine kinases. Science. 1995;268:251–5. [PubMed]
7. Thompson BJ, Buonamici S, Sulis ML, Palomero T, Vilimas T, Basso G, et al. The SCFFBW7 ubiquitin ligase complex as a tumor suppressor in T cell leukemia. J Exp Med. 2007;204:1825–35. [PMC free article] [PubMed]
8. Rhee Y, Gurel F, Gafni Y, Dingwall C, Citovsky V. A genetic system for detection of protein nuclear import and export. Nature Biotech. 2000;18:433–7. [PubMed]
9. Fujii H, Ogasawara K, Otsuka H, Suzuki M, Yamamura K-i, Yokochi T, et al. Functional dissection of the cytoplasmic subregions of the IL-2 receptor βc chain in primary lymphocyte populations. EMBO J. 1998;17:6551–7. [PubMed]
10. Hoshino A, Matsumura S, Kondo K, Hirst JA, Fujii H. Inducible translocation trap: a system for detecting inducible nuclear translocation. Mol Cell. 2004;15:153–9. [PubMed]
11. Onishi M, Kinoshita S, Morikawa Y, Shibuya A, Phillips J, Lanier LL, et al. Applications of retrovirus-mediated expression cloning. Exp Hematol. 1996;24:324–9. [PubMed]
12. Giri JG, Ahdieh M, Eisenman J, Shanebeck K, Grabstein K, Kumaki S, et al. Utilization of the β and γ chains of the IL-2 receptor by the novel cytokine IL-15. EMBO J. 1994;13:2822–30. [PubMed]
13. Takeshita T, Asao H, Ohtani K, Ishii N, Kumaki S, Tanaka N, et al. Cloning of the γ chain of the human IL-2 receptor. Science. 1992;257:379–82. [PubMed]
14. Hoshino A, Hirst JA, Fujii H. Regulation of cell proliferation by interleukin-3-induced nuclear translocation of pyruvate kinase. J Biol Chem. 2007;282:17706–11. [PubMed]
15. Gossen M, Freundlieb S, Bender G, Muller G, Hillen W, Bujard H. Transcriptional activation by tetracyclines in mammalian cells. Science. 1995;268:1766–9. [PubMed]
16. Miyazaki T, Kawahara A, Fujii H, Nakagawa Y, Minami Y, Liu Z-J, et al. Functional activation of Jak1 and Jak3 by selective association with IL-2 receptor subunits. Science. 1994;266:1045–7. [PubMed]
17. Shibuya H, Yoneyama M, Ninomiya-Tsuji J, Matsumoto K, Taniguchi T. IL-2 and EGF receptors stimulate the hematopoietic cell cycle via different signaling pathways: demonstration of a novel role for c-myc. Cell. 1992;70:57–67. [PubMed]
18. Hoshino A, Fujii H. Temporal regulation of Stat5 activity determines cell differentiation program. Biochem Biophys Res Commun. 2007;358:914–9. [PMC free article] [PubMed]
19. Rand MD, Grimm LM, Artavanis-Tsakonas S, Patriub V, Blacklow SC, Sklar J, et al. Calcium depletion dissociates and activates heterodimeric Notch receptors. Mol Cell Biol. 2000;20:1825–35. [PMC free article] [PubMed]
20. Giri JG, Kumaki S, Ahdieh M, Friend DJ, Loomis A, Shanebeck K, et al. Identification and cloning of a novel IL-15 binding protein that is structurally related to the α chain of the IL-2 receptor. EMBO J. 1995;14:3654–63. [PubMed]
21. Pear WS, Aster JC, Scott ML, Hasserjian RP, Soffer B, Sklar J, et al. Exclusive development of T cell neoplasms in mice transplanted with bone marrow expressing activated Notch alleles. J Exp Med. 1996;183:2283–91. [PMC free article] [PubMed]