Expression pattern of c-fes oncogene mRNA in human myeloid cells

Spatial and temporal changes in the subcellular localization of the nuclear protein-tyrosine kinase, c-Fes

Tyrosine phosphorylation has emerged as a mechanism to control cellular events in the nucleus. The c-Fes protein-tyrosine kinase is an important regulator of cell growth and differentiation in several cell types, and is found in the nucleus of hematopoietic cells. In this study, we showed nuclear localization of c-Fes in both hematopoietic (K562, TF-1, HEL, U937, and HL-60) and nonhematopoietic cell lines (293T, CaOv3, TfxH, MG-63, HeLa, DU-145) by immunofluorescence and confocal microscopy. c-Fes showed striking changes in subcellular localization at specific stages of mitosis. In interphase cells, the intranuclear distribution of c-Fes was diffuse with occasional bright foci. Some c-Fes was present in the cytosol after breakdown of the nuclear membrane, in prometaphase. At prometaphase and metaphase c-Fes was also associated with the chromosomes, in a punctate pattern that partially overlapped with the centromere. Further comparison with proteins that are known components of the kinetochore suggested that some c-Fes protein was located at the centromeric alpha-satellite DNA, between the kinetochores. At anaphase and telophase, c-Fes was entirely cytoplasmic and no protein was found associated with the chromosomes. The timing of c-Fes' appearance at the centromere coincides with the period of kinetochore assembly. These data suggest that c-Fes is recruited to the kinetochore during mitosis.

Expression of c-Fes Protein Isoforms Correlates with Differentiation in Myeloid Leukemias

The cellular fes gene encodes a 93-kilodalton protein-tyrosine kinase (p93) that is expressed in both normal and neoplastic myeloid cells. Increased c-Fes expression is associated with differentiation in normal myeloid cells and cell lines. Our hypothesis was that primary leukemia cells would show a similar pattern of increased expression in more differentiated cells. Therefore, we compared c-Fes expression in cells with an undifferentiated, blast phenotype (acute myelogenous leukemia--AML) to cells with a differentiated phenotype (chronic myelogenous leukemia--CML). Instead of differences in p93 expression levels, we found complex patterns of c-Fes immunoreactive proteins that corresponded with differentiation in normal and leukemic myeloid cells. The "blast" pattern consisted of c-Fes immunoreactive proteins p93, p74, and p70; the "differentiated" pattern showed two additional c-Fes immunoreactive proteins, p67 and p62. Using mRNA from mouse and human cell lines, we found deletion of one or more exons in the c-fes mRNA. Those deletions predicted truncation of conserved domains (CDC15/FCH and SH2) involved in protein-protein interactions. No deletions were found, however, within the kinase domain. We infer that alternative splicing generates a family of c-Fes proteins. This may be a mechanism to direct the c-Fes kinase domain to different subcellular locations and/or substrates at specific stages of myeloid cell differentiation.

A minimal c-fes cassette directs myeloid-specific expression in transgenic mice

The c-fes proto-oncogene encodes a 92-kd protein tyrosine kinase whose expression is restricted largely to myeloid and endothelial cells in adult mammals. A 13.2-kilobase (kb) humanc-fes genomic fragment was previously shown to containcis-acting element(s) sufficient for a locus control function in bone marrow macrophages. Locus control regions (LCRs) confer transgene expression in mice that is integration site independent, copy number dependent, and similar to endogenous murine messenger RNA levels. To identify sequences required for this LCR,c-fes transgenes were analyzed in mice. Myeloid-cell–specific, deoxyribonuclease-I–hypersensitive sites localized to the 3′ boundary of exon 1 and intron 3 are required to confer high-level transgene expression comparable to endogenous c-fes, independent of integration site. We define a minimal LCR element as DNA sequences (nucleotides +28 to +2523 relative to the transcription start site) located within intron 1 to intron 3 of the human locus. When this 2.5-kb DNA fragment was linked to a c-fes complementary DNA regulated by its own 446–base-pair promoter, integration-site–independent, copy-number–dependent transcription was observed in myeloid cells in transgenic mice. Furthermore, this 2.5-kb cassette directed expression of a heterologous gene (enhanced green fluorescent protein) exclusively in myeloid cells. The c-fes regulatory unit represents a novel reagent for targeting gene expression to macrophages and neutrophils in transgenic mice.

A minimal c-fes cassette directs myeloid-specific expression in transgenic mice

The c-fes proto-oncogene encodes a 92-kd protein tyrosine kinase whose expression is restricted largely to myeloid and endothelial cells in adult mammals. A 13.2-kilobase (kb) humanc-fes genomic fragment was previously shown to containcis-acting element(s) sufficient for a locus control function in bone marrow macrophages. Locus control regions (LCRs) confer transgene expression in mice that is integration site independent, copy number dependent, and similar to endogenous murine messenger RNA levels. To identify sequences required for this LCR,c-fes transgenes were analyzed in mice. Myeloid-cell–specific, deoxyribonuclease-I–hypersensitive sites localized to the 3′ boundary of exon 1 and intron 3 are required to confer high-level transgene expression comparable to endogenous c-fes, independent of integration site. We define a minimal LCR element as DNA sequences (nucleotides +28 to +2523 relative to the transcription start site) located within intron 1 to intron 3 of the human locus. When this 2.5-kb DNA fragment was linked to a c-fes complementary DNA regulated by its own 446–base-pair promoter, integration-site–independent, copy-number–dependent transcription was observed in myeloid cells in transgenic mice. Furthermore, this 2.5-kb cassette directed expression of a heterologous gene (enhanced green fluorescent protein) exclusively in myeloid cells. The c-fes regulatory unit represents a novel reagent for targeting gene expression to macrophages and neutrophils in transgenic mice.

CD30 ligand (CD30L)-expressing acute myeloid leukemias: a new model of paracrine interactions for the regulation of blast cells proliferation

CD30 ligand (CD30L) is a type-II membrane glycoprotein capable of transducing signals through its specific counterstructure CD30. Even though there are indications that CD30L plays a key role as a paracrine-acting surface molecule in the deregulated cytokine cascade of Hodgkin's disease, little is known about its biological functions in other human hemopoietic malignancies, despite the demonstration of the frequent expression of CD30L in hemopoietic neoplasms of both myeloid and lymphoid origin. The present review summarises structural and biological properties of CD30L, and focuses on CD30L+ acute myeloid leukemias (AMLs) by recapitulating some phenotypic and clinical features of this subset of acute leukemias. We also discuss some mechanisms by which CD30L-expressing leukemic blasts may gain a proliferative advantage through direct interaction with specific cells, in turn expressing its specific counterreceptor CD30. In particular, data has been provided suggesting that CD30L+ AMLs may evoke a sort of polarized T-cell response with the preferential production of Th2-like cytokines, mainly IL-4, by specific CD30-expressing T cell subsets. On the other hand, leukemic blasts presenting surface CD30L, have been shown to express a peculiar cytokine-receptors pattern that makes them an ideal target for T cells-produced Th2-like cytokines. Furthermore, some Th2-like cytokines, such as IL-4, are able to enhance blast cells proliferation, as well as to up-regulate the surface expression of specific adhesion molecules that have been shown to be associated with the presence of CD30L on AML blasts.

Expression of two myeloid cell-specific genes requires the novel transcription factor, c-fes expression factor

The protein product of the c-fes proto-oncogene has been implicated in the normal development of myeloid cells (macrophages and granulocytes). We have previously shown that 151 base pairs of c-fes 5'-flanking sequences are sufficient for myeloid cell-specific expression and include functional binding sites for Sp1, PU.1, and a novel nuclear factor (Heydemann, A., Juang, G., Hennessy, K., Parmacek, M. S., and Simon, M. C. (1996) Mol. Cell. Biol. 16, 1676-1686). This novel hematopoietic transcription factor, termed FEF (c-fes expression factor), binds to a cis-acting element that is located at nucleotides -9 to -4 of the c-fes promoter between two Ets binding sites (at -19 to -15 and -4 to +1) which bind PU.1. We now show that a FEF binding site exists in the myeloid cell-specific regulatory region of a second gene, the -2.7-kilobase pair enhancer of chicken lysozyme. The lysozyme FEF site is immediately 5' to a PU. 1 site, analogous to their arrangement in the c-fes promoter, and allows the formation of a preliminary FEF consensus site, 5'-GAAT(C/G)A-3'. This consensus site does not match any sites for known transcription factors. Importantly, although PU.1 binds immediately 3' of the FEF site in both the c-fes promoter and the chicken lysozyme enhancer (CLE), we show that they bind independently. The FEF sites are required for high levels of transcription by both the CLE and the c-fes promoter in transient transfection experiments. Importantly, elimination of the CLE FEF site abolishes all transcriptional activity of this enhancer element. Mutation of the adjacent PU.1 site in either the c-fes promoter or the CLE, reduces activity by approximately 50%. Therefore, transcription of both lysozyme and fes in myeloid cells requires FEF and PU.1. UV cross-linking experiments show that the FEF binding activity consists of a single 70-kDa protein in both human and murine cell lines. FEF binding activity is not affected by antibodies that specifically recognize a number of cloned transcription factors. Collectively, these data indicate that we have identified a novel transcription factor that is functionally important for the expression of at least two myeloid cell-specific genes.

A Tyrosine-Phosphorylated Protein of 140 kD Is Constitutively Associated With the Phosphotyrosine Binding Domain of Shc and the SH3 Domains of Grb2 in Acute Myeloid Leukemia Cells

The Shc gene encodes three proteins that have been implicated as mediators of signal transduction from growth factor receptors and nonreceptor tyrosine kinases to Ras. Overexpression of Shc in established murine fibroblasts results in oncogenic transformation, indicating that Shc has oncogenic potential. Shc proteins contain a carboxy terminal SH2 domain and a novel non-SH2 phosphotyrosine-binding (PTB) domain that specifically recognizes a phosphorylated NPXpY motif in target proteins such as the epidermal growth factor receptor. We show here that Shc is constitutively tyrosine-phosphorylated in all primary acute myeloid leukemias analyzed and that, in some of these leukemias, Shc is associated through its PTB domain with a tyrosinephosphorylated protein of 140 kD (p140) in vivo. In factor-dependent cells, this 140-kD protein can be tyrosine-phosphorylated in vitro in response to cytokines involved in myeloid proliferation and differentiation, ie, granulocyte-macrophage colony-stimulating factor and colony-stimulating factor-1. A similar or identical protein of 140 kD is constitutively bound to the C-terminal SH3 domain of Grb2 in the same acute myeloid leukemias. In addition to p140, other tyrosine-phosphorylated proteins of 61 and 200 kD are constitutively associated with Shc in some of the leukemias analyzed. Our results implicate Shc, Grb2, p140, and additional tyrosine-phosphorylated proteins of 61 and 200 kD in signalling of acute myeloid leukemia cells.

Leukocyte protein tyrosine kinases: potential targets for drug discovery

Intracellular signal transduction following the extracellular ligation of a wide variety of different types of surface molecules on leukocytes involves the activation of protein tyrosine kinases. The dependence of successful intracellular signaling on the functions of the nontransmembrane class of protein tyrosine kinases coupled with the cell type-specific expression patterns for several of these enzymes makes them appealing targets for therapeutic intervention. Development of drugs that can interfere with the catalytic functions of the nontransmembrane protein tyrosine kinases or that can disrupt critical interactions with regulatory molecules and/or substrates should find clinical applications in the treatment of allergic diseases, autoimmunity, transplantation rejection, and cancer.

Analysis of Fes kinase activity in myeloid cell growth and differentiation

Fes is a nonreceptor protein tyrosine kinase that has been implicated in a variety of cytokine signal transduction pathways, as well as differentiation of myeloid cells. To address the role of Fes in these processes, we overexpressed a kinase-defective Fes protein in the factor-dependent cell-lines, TF-1 and 32D. Proliferative responses to GM-CSF and interleukin 3, and the induction of differentiation by G-CSF were not altered by expression of the kinase mutant Fes protein, indicating that Fes kinase activity is not critical for these biological events in these cell lines.

Microsatellite instability in IVS3 of murine c-fes gene: tumor-associated rearrangement and mammalian divergence

The murine lymphomacrophage hybrids ESb, EbF1, EbF2-c4, which express c-fes constitutively, were found by Southern analysis to bear a c-fes deletion of almost 100 bp. The deleted allele was transmitted to the metastatic hybrids by their nonexpressing, poorly metastatic T-lymphoma progenitor Eb, which also has a structurally normal c-fes allele. PCR amplification and sequencing of fes cDNA spanning exons 3-5, where the deletion mapped, ruled out any involvement of coding sequences in the rearrangement. PCR amplification of the as yet unsequenced murine c-fes IVS3 and IVS4 showed they are about 50% longer than their human and feline homologs. Sequencing of IVS4 showed no difference between tumor and control DNA. Sequencing of part of the approximately 2600-bp IVS3 was guided by the restriction analysis of PCR products from control and hybrid DNAs. This showed that differences from the control appeared to be mainly located in the 900-bp HindIII-EcoRI fragment, localized in the middle of IVS3. As all three hybrids had the same restriction map, this fragment was sequenced in one of them (ESb). A run of >200 CA repeats was found in control DNA, and a reduction in the CAn microsatellite accounted for most of the c-fes deletion in the ESb hybrid. Interestingly, the 50% reduction in the size of human and feline c-fes IVS3 as compared with the murine homolog is mostly due to contraction of the same microsatellite.

The myeloid-cell-specific c-fes promoter is regulated by Sp1, PU.1, and a novel transcription factor

The protein product of the c-fps/fes (c-fes) proto-oncogene has been implicated in the normal development of myeloid cells (macrophages and neutrophils). mRNA for c-fes has been detected exclusively in myeloid cells and vascular endothelial cells in adult mammals. Although a 13-kilobase-pair (kb) human c-fes transgene exhibits high levels of expression in mice, the sequences that confer myeloid-cell-specific expression of the human c-fes gene have not been defined. Transient-transfection experiments demonstrated that plasmids containing 446 bp of c-fes 5'-flanking sequences linked to a luciferase reporter gene were active exclusively in myeloid cells. No other DNA element within the 13-kb human c-fes locus contained positive cis-acting elements, with the exception of a weakly active region within the 3'-flanking sequences. DNase I footprinting assays revealed four distinct sites that bind myeloid nuclear proteins (-408 to -386, -293 to -254, -76 to -65, and -34 to +3). However, the first two footprints resided in sequences that were largely dispensable for transient activity. Plasmids containing 151 bp of 5'-flanking sequences confer myeloid-cell-specific gene expression. Electrophoretic mobility shift analyses demonstrated that the 151-bp region contains nuclear protein binding sites for Sp1, PU.1, and/or Elf-1, and a novel factor. This unidentified factor binds immediately 3' of the PU.1/Elf-1 sites and appears to be myeloid cell specific. Mutation of the PU.1/Elf-1 site or the 3' site (FP4-3') within the context of the c-fes promoter resulted in substantially reduced activity in transient transfections. Furthermore, transient-cotransfection assay demonstrated that PU.1 (and not Elf-1) can transactivate the c-fes promoter in nonmyeloid cell lines. We conclude that the human c-fes gene contains a strong myeloid-cell-specific promoter that is regulated by Sp1, PU.1, and a novel transcription factor.

Role of c-Fes in normal and neoplastic hematopoiesis

The study of oncogenes has provided numerous insights, not only into the mechanisms by which growth regulation becomes uncontrolled in cancer cells, but also into signal transduction processes which regulate the orderly proliferation and maturation of cells. c-fes/fps is a cellular oncogene which has been transduced frequently by mammalian and avian retroviruses. There are several features about Fes which suggest it may play a unique role in myeloid cell growth and differentiation. While it contains a tyrosine kinase and SH2 domain, there is no SH3 domain or carboxy terminal regulatory phosphotyrosine such as found in the Src family of kinases. Fes has a unique N-terminal domain of over 400 amino acids of unknown function. It has been implicated in signaling by a variety of hematopoietic growth factors, and is predominantly a nuclear protein.

Activation of c-fos and c-fes in metastatic lympho-macrophage hybrids

The expression of proto-oncogenes involved in myelomonocytic differentiation was studied in 3 metastatic murine lympho-macrophage hybrids (ESb, EbF1, EbF2-C4) which display several antigenic and functional macrophage properties. Constitutive expressions of fos and fesmRNA, which were not detectable in the weakly metastatic parent lymphoma (Eb), was shown in all the proliferating hybrid lines. By contrast, c-myc and c-myc expressions were shared by the tumor parent and the hybrids. The c-fos transcripts observed in the hybrids were atypical in size, 2.3 kb, but standard 2.2-kb transcripts could be detected in serum-induced cells, even in the non-expressing Eb lymphoma. The kinetics of the induced fos mRNA was found to conform to the features reported in the literature for a large variety of cells. No structural alteration of the c-fos gene was detected by Southern analysis. PCR amplification of the 2.3- and 2.2-kb fos mRNA showed that they are identical in size in both the coding and the 3' untranscribed region. A longer poly A tail is thought to account for the additional 100 bp in the 2.3-kb fos mRNA, as both the 2.3- and 2.2-kb transcripts attain the same size following de-adenylation.

Regulation of hematopoietic cell function by protein tyrosine kinase-encoding oncogenes, a review

Tyrosine phosphorylation of proteins by protein tyrosine kinases (PTKs) is an important mechanism in the regulation of various cellular processes such as proliferation, differentiation, and transformation. Accumulating data implicate PTKs as essential intermediates in the transduction of extracellular signals to the interior of the cell. This review summarizes the mechanism of action of PTKs from the major subclasses and the involvement of PTK-encoding oncogenes in the regulation of hematopoietic cell function.

Differentiation stage specificity of tyrosine phosphorylation in response to granulocyte macrophage colony stimulating factor (GM-CSF)

We have previously described differentiation associated tyrosine protein kinase activity in WEHI-3B monomyelocytic leukemia cells and have presented evidence which suggests that this activity may not be involved in the initiation of the differentiation process, but more likely has a functional role in the mature myeloid cell. The present study was undertaken in an attempt to identify the protein(s) responsible for the tyrosine protein kinase activity and to seek a potential role for this activity in the mature cell. We and others have detected the p92c-fes tyrosine protein kinase in WEHI-3B cells. This protein has been implicated in myeloid differentiation, as well as in the transduction of signals in response to granulocyte macrophage colony stimulating factor (GM-CSF). Thus, it was of interest to determine whether tyrosine phosphorylation may be involved in the response of WEHI-3B cells to GM-CSF. Treatment of differentiated WEHI-3B D+ cells with GM-CSF was found to result in the tyrosine phosphorylation of a number of endogenous cellular proteins in a concentration-dependent, rapid and transient manner. In contrast, the cytokine did not elicit such a response in undifferentiated cells, despite the fact that undifferentiated cells have been reported to possess GM-CSF receptors. These findings are consistent with the concept that the effects of GM-CSF on differentiated myeloid cells are mediated through tyrosine phosphorylation, that only differentiated cells are competent to accomplish this event, and that this response constitutes at least one functional role for the myeloid differentiation associated tyrosine protein kinase activity.

Partial characterization of protein tyrosine kinase activity in normal and leukemic human myeloid cells

We have examined the expression of the protein tyrosine kinase (PTK) encoding oncogenes fes and abl in normal and malignant human myeloid cells in immunoblotting experiments. fes was markedly present in all cytosolic and most membrane fractions of normal and malignant cells. abl was only visible in normal cells, and occurred mostly in the cytosolic fractions. Molecular weights of identified proteins were different from the known products of fes and abl, possibly by alternative splicing at the mRNA level or by proteolysis. PTKs in myeloid cells were further purified by fast liquid protein chromatography (FPLC). PTK-activities of column fractions were assayed using a solid-phase non-radioactive dot-blot assay. Cytosolic and membrane fractions showed a FPLC pattern with a constant as well as a variable part in both normal and malignant cells, possibly indicative for PTKs with specialized functions in normal cell growth and transformation. Partial characterization of PTKs from different eluted peaks of AML-M4 blast cells demonstrated that PTKs from these peaks are kinetically distinct from each other.

Expression of the c-fes proto-oncogene in granulocyte-macrophage colony-stimulating factor-dependent acute myelogenous leukemia cells grown autonomously

In the present article, we show that 6 of 69 acute myelogenous leukemia (AML) samples exhibited autonomous in vitro growth that was dependent on endogenous granulocyte-macrophage colony-stimulating factor (GM-CSF). Cytoplasmic RNA harvested from all 6 leukemia specimens contained GM-CSF transcripts easily detectable by mRNA hybridization. All 6 GM-CSF-expressing leukemia samples simultaneously displayed high levels of transcripts for the c-fes proto-oncogene previously shown to be expressed in GM-CSF sensitive myeloid cells, whereas only 2 of the 48 AML samples not expressing GM-CSF accumulated c-fes mRNA. Seven of additional 14 GM-CSF-expressing specimens showed specific signals upon RNA hybridization with the c-fes probe, but failed to grow autonomously. These results suggest that c-fes and GM-CSF genes may be coordinately regulated in AML blasts and that GM-CSF-mediated growth autonomy may be linked to c-fes expression.