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D A Liebermann

Publications and source records attributed to D A Liebermann.

At least 37 records · Page 2Linked to original sources
PubMed1998

AP-1 (Fos/Jun) transcription factors in hematopoietic differentiation and apoptosis.

A combination of in vitro and in vivo molecular genetic approaches have provided evidence to suggest that AP-1 (Fos/Jun) transcription factors play multiple roles in functional development of hematopoietic precursor cells into mature blood cells along most, if not all, of the hematopoietic cell lineages. This includes the monocyte/macrophage, granulocyte, megakaryocyte, mastocyte and erythroid lineages. In addition, studies using c-fos knockout mice have established a unique role for Fos, as a member of the AP-1 transcription factor complex, in determining the differentiation and activity of progenitors of the osteoclast lineage, a population of bone-forming cells which are of hematopoietic origin as well. Evidence has also accumulated to implicate AP-1 (Fos/Jun) transcription factor complexes as both positive and negative modulators of distinct apoptotic pathways in many cell types, including cells of hematopoietic origin. Fos/Jun have been implicated as positive modulators of apoptosis induced in hematopoietic progenitor cells of the myeloid lineage, a function that may relate to the control of blood cell homeostasis, as well as in programmed cell death associated with terminal differentiation of many other cell types, and apoptosis associated with withdrawal of growth/survival factors. On the other hand, the study of apoptosis induced in mammalian cells has implicated AP-1 in the protection against apoptosis induced by DNA-damaging agents. However, evidence to the contrary has been obtained as well, suggesting that AP-1 may function to modulate stress-induced apoptosis either positively or negatively, depending on the microenvironment and the cell type in which the stress stimulus is induced.

Animals↗
PubMed1998

Role of a mutant p53 protein in apoptosis: characterization of a function independent of transcriptional trans-activation.

Wild-type (wt) tumor suppressor p53 has been implicated in cellular radiosensitivity, mediated by its role in apoptosis and growth arrest. Intriguingly, it was observed that the temperature sensitive (ts) mutant p53val135 protein functions as a positive modulator of cellular radiosensitivity, as evident from acceleration of irradiation-induced apoptosis of M1p53ts (p53val135) cells at the non-permissive temperature; this effect was correlated with acceleration of exit from the G2 checkpoint of the cell cycle. In this work it is shown that the ability of mutant p53val135 to accelerate irradiation-induced apoptosis, at the non-permissive temperature, was devoid of transcriptional trans-activation of p53 target genes. In contrast, the apoptotic function of wt p53val135 was observed to include components which are both dependent and independent of transcriptional trans-activation. Taken together, these observations suggest that mutant p53val135 protein retains the apoptotic component of wt p53 that is devoid of transcriptional trans-activation, and that, although this activity is insufficient to induce apoptosis on its own, it can cooperate to accelerate DNA damage-induced cell death. The results of this work contribute to a better understanding of the complexity of the apoptotic response elicited by wt p53, and highlight the potential role of mutant p53 proteins, as well as trans-activation independent apoptosis, in tumor suppression by irradiation therapy.

Animals↗
PubMed1997

Lineage-specific regulation of hematopoiesis by HOX-B8 (HOX-2.4): inhibition of granulocytic differentiation and potentiation of monocytic differentiation.

Homeobox proteins comprise a major class of transcription factors, which have been implicated in normal hematopoiesis and leukemogenesis. Notable in this context is the homeobox gene HOX-B8 (formerly known as HOX-2.4), which was shown to cooperate with hematokines to induce leukemia, and to enhance self-renewal of immature myeloid progenitors when expressed alone. How HOX-B8 may affect lineage specific development of hematopoietic progenitor cells is unknown. Here it is shown that ectopic expression of HOX-B8 specifically inhibited dimethyl sulfoxide (DMSO)-induced granulocytic differentiation of autonomously proliferating HL-60 myeloid progenitor cells. HOX-B8 also inhibited the granulocyte colony-stimulating factor (G-CSF)-induced granulocytic developmental program of factor dependent 32Dcl3 hematopoietic progenitors, including survival, proliferation, and differentiation, as evident by rapid apoptosis of the cells following removal of interleukin-3 (IL-3) and addition of G-CSF. In sharp contrast, HOX-B8 had no effect on macrophage differentiation of M1 and HL-60 cells induced by IL-6 and phorbol-12-myristate-13-acetate, respectively. Moreover, HOX-B8 expression endowed the 32Dcl3 cells with the ability to be induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) for terminal differentiation exclusively along the macrophage lineage; this effect was at least partially mediated via expression of the zinc finger transcription factor Egr-1. Thus, ectopic expression of HOX-B8 in hematopoietic progenitor cells appears to differentially affect lineage specific development, negatively regulating granulocyte development and positively regulating macrophage development.

Animals↗
PubMed1996

The differentiation primary response gene MyD118, related to GADD45, encodes for a nuclear protein which interacts with PCNA and p21WAF1/CIP1.

Towards dissecting the regulation of terminal differentiation, including growth arrest and apoptosis, myeloid differentiation primary response (MyD) genes, induced in the absence of de novo protein synthesis following induction of M1 myeloblastic leukemia cells for terminal differentiation have been isolated. MyD118 was one of the novel MyD genes cloned, subsequently observed also to be a primary response gene to TGF-beta, which induces M1 cells for growth arrest and apoptosis uncoupled from differentiation. The MyD118 encoded protein was observed to be remarkably similar to the protein encoded by Gadd45, a growth arrest and DNA damage induced gene, regulated in part by the tumor suppressor p53. Though evidence has accumulated that MyD118 functions as an important modulator of negative growth control both in hematopoietic and non-hematopoietic cells, its mechanism of action is unknown. To better understand the role(s) of MyD118 in negative growth control, we have analysed the expression and biological characteristics of the MyD118 protein, compared to the Gadd45 protein, in distinct pathways of growth arrest and apoptosis, including p53 dependent and independent pathways either coupled or uncoupled from differentiation. It is shown that MyD118 and Gadd45 differentially accumulated upon induction of distinct pathways of growth arrest and apoptosis; notably, MyD118, but not Gadd45, was induced by TGF-beta, whereas Gadd45, but not MyD118, was induced by activating wild type (wt) p53 function. It is also shown that MyD118 is a nuclear protein, which regardless of the pathway induced, predominantly localized within the cell nucleus, and interacted with the DNA replication and repair protein PCNA and the cyclin dependent kinase inhibitor P21WAF1/CIP1. MyD118 also modestly stimulated DNA repair in vitro. All of these characteristics were shared with Gadd45. Finally, it is demonstrated that MyD118, Gadd45 and p21 synergized in the suppression of colony formation by NIH3T3 cells. Taken together, these findings demonstrate that MyD118 and Gadd45 are representative of a new protein family that share remarkable functional similarities in the control of distinct pathways of negative growth, including the suppression of cellular growth and programmed cell death.

3T3 Cells↗
PubMed1996

Activated abl oncogenes and apoptosis: differing responses of transformed myeloid progenitor cell lines.

Activation of the c-abl protooncogene occurs during the generation of both the Abelson murine leukemia virus and the bcrabl fusion gene. To further dissect the biological properties of these proteins, we studied their effect on apoptosis. Using dimethyl sulfoxide (DMSO) to induce apoptosis in the murine myeloid progenitor cell line 32Dcl3, we examined the effect of expression of both v-abl and bcrabl transgenes on apoptosis. v-abl expressing 32Dcl3 cells are sensitive to apoptosis induction, similar to parental 32Dcl3 cells. In contrast, bcrabl expression 32Dcl3 cells are protected from the apoptotic stimulus resulting from DMSO exposure. Analyzing the expression patterns for Bcl-2 and Bax, two proteins known to modulate the apoptotic response, we found a downregulation of Bcl-2 and enhanced expression of Bax in 32Dcl3 cells. In 32Dcl3/v-Abl cells, Bcl-2 expression remained constant while Bax was upregulated, whereas in 32Dcl3 cells expressing bcrabl, there was continuous expression of Bcl-2 at a level greater than observed in v-abl transformed cells. Taken together, our data demonstrate that although both activated abl gene products promote overlapping effects of some biological responses (i.e., factor-independent proliferation) they diverge in their effect on apoptotic signaling pathways.

Animals↗
PubMed1996

The carboxyl terminus of the murine MyD116 gene substitutes for the corresponding domain of the gamma(1)34.5 gene of herpes simplex virus to preclude the premature shutoff of total protein synthesis in infected human cells.

The herpes simplex virus 1 mutants from which both copies of the gamma(1)34.5 gene had been deleted trigger total shutoff of protein synthesis in human neuroblastoma cells and human foreskin fibroblasts but not in African green monkey (Vero) cells. The carboxyl-terminal 64 amino acids of gamma(1)34.5 are homologous to the corresponding domain of MyD116, a murine myeloid differentiation primary responsive gene. The carboxyl-terminal domain of gamma(1)34.5 is required to preclude the shutoff of protein synthesis (J. Chou and B. Roizman, Proc. Natl. Acad. Sci. USA 91:5247-5251, 1994). We report that in-frame substitution of the carboxyl terminus of gamma(1)34.5 with the corresponding domain of MyD116 in the context of the viral genome restored the ability of gamma(1)34.5 to preclude premature shutoff of protein synthesis in both neuroblastoma cells and in human foreskin fibroblasts. The results suggest that (i) in the course of its evolution, the virus "borrowed" a gene fragment to preclude a cell response to infection and (ii) the carboxyl terminus of MyD116 and its family of genes known as GADD34 may have a similar function(s) in cells stressed by growth arrest, DNA damage, and differentiation and in herpes simplex virus infection.

Animals↗
PubMed1995

Blocking c-Myc and Max expression inhibits proliferation and induces differentiation of normal and leukemic myeloid cells.

Given the central role c-Myc plays in growth control, differentiation and apoptosis, understanding how c-Myc functions will increase our understanding about normal cell development, and how alterations in these processes can lead to malignancy. C-Myc is a negative regulator of terminal myeloid differentiation; therefore, it was of interest to determine what effect blocking c-Myc expression would have on proliferation and differentiation. In this work we showed that blocking expression of either c-Myc or Max, its molecular partner, in myeloblastic leukemia M1 cells activated the differentiation program in the absence of an exogenous source of differentiation inducer; the cells assumed an intermediate stage myeloid morphology. Moreover, when both c-Myc and Max expression was concommitantly blocked, many of the cells underwent terminal differentiation. Finally, extending these studies to myeloblast enriched normal bone marrow (BM) cell has shown that blocking expression of either c-Myc or Max accelerated GM-CSF-induced differentiation along both the granulocytic and monocytic lineages. Thus, it can be concluded that blocking either c-Myc or Max expression in myeloid cells at specific stages of development activates and accelerates the terminal differentiation program.

Animals↗
PubMed1995

Molecular controls of growth arrest and apoptosis: p53-dependent and independent pathways.

Cell homeostasis is regulated by a balance between proliferation, growth arrest and programmed cell death (apoptosis). Until recently, studies on oncogenesis have focused on the regulation of cell proliferation. The recognition that negative growth control, including growth arrest and programmed cell death, must be understood to comprehend how appropriate cell numbers are maintained and how alterations in any part of the equation can contribute to malignancy has led to a burst of work in this field. This review focuses on what has been learned about distinct settings of negative growth control, analyzing p53-dependent and independent pathways of growth arrest and apoptosis either coupled or uncoupled from differentiation, with an emphasis on the use of hematopoietic cells. The importance of understanding the molecular biology of apoptotic and growth arrest pathways in cancer therapy, and future directions to study negative growth control are addressed as well.

Animals↗
PubMed1995

p53 involvement in control of G2 exit of the cell cycle: role in DNA damage-induced apoptosis.

DNA damage in proliferating mammalian cells induces a complex cellular response comprising perturbation of the cell cycle and programmed cell death. The relationship between p53-dependent and p53-independent apoptotic cell death, as well as the cell cycle checkpoints induced by DNA damaging agents were explored in hematopoietic cells, using M1 myeloblastic leukemia cells, which are null for p53 expression, genetically engineered M1 variants, expressing p53ts and bcl-2 transgenes, as well as myeloblast enriched bone-marrow cells obtained from wild type p53 (wt p53) and p53-deficient mice. It is shown that gamma-irradiation of M1p53ts cells activated a function of the temperature sensitive mutant transgene p53 (p53ts), promoting increased apoptosis relative to parental, null p53 M1 cells. It is also shown that the kinetics of apoptotic cell death induced by gamma-irradiation correlated with the rapidity of exit from gamma-ray-induced G2 arrest for all the different hematopoietic cell types indicated above. Finally, data has been obtained to demonstrate that, in addition to a role in apoptosis and G1 arrest, wild-type p53 positively modulated the exit from the gamma-ray-induced G2 checkpoint. Taken together, these findings indicate that this new function for p53 is a component of the physiological pathway by which p53 exerts its role in apoptosis.

Animals↗
PubMed1995

Dissection of the genetic programs of p53-mediated G1 growth arrest and apoptosis: blocking p53-induced apoptosis unmasks G1 arrest.

Employing the myeloblastic leukemia M1 cell line, which does not express endogenous p53, and genetically engineered variants, it was recently shown that activation of p53, using a p53 temperature-sensitive mutant transgene (p53ts), resulted in rapid apoptosis that was delayed by high level ectopic expression of bcl-2. In this report, advantage has been taken of these M1 variants to investigate the relationship between p53-mediated G1 arrest and apoptosis. Flow cytometric cell cycle analysis has provided evidence that activation of wild-type (wt) p53 function in M1 cells resulted in the induction of G1 growth arrest; this was clearly seen in the M1p53/bcl-2 cells because of the delay in apoptosis that unmasked p53-induced G1 growth arrest. This finding was further corroborated at the molecular level by analysis of the expression and function of key cell cycle regulatory genes in M1p53 versus M1p53/bcl-2 cells after the activation of wt p53 function; events that take place at early times during the p53-induced G1 arrest occur in both the M1p53 and the M1p53/bcl-2 cells, whereas later events occur only in the M1p53/bcl-2 cells, which undergo delayed apoptosis, thereby allowing the cells to complete G1 arrest. Finally, it was observed that a spectrum of p53 target genes implicated in p53-induced growth suppression and apoptosis were similarly regulated, either induced (gadd45, waf1, mdm2, and bax) or suppressed (c-myc and bcl-2), after activation of wt p53 function in M1p53 and M1p53/bcl-2 cells. Taken together, these findings show that wt p53 can simultaneously induce the genetic programs of both G1 growth arrest and apoptosis within the same cell type, in which the genetic program of cell death can proceed in either G1-arrested (M1p53/bcl-2) or cycling (M1p53) cells. These findings increase our understanding of the functions of p53 as a tumor suppressor and how alterations in these functions could contribute to malignancy.

Animals↗
PubMed1995

The zinc finger transcription factor Egr-1 potentiates macrophage differentiation of hematopoietic cells.

Previously we have shown that the zinc finger transcription factor Egr-1 is essential for and restricts differentiation of hematopoietic cells along the macrophage lineage, raising the possibility that Egr-1 actually plays a deterministic role in governing the development of hematopoietic precursor cells along the monocytic lineage. To test this hypothesis, we have taken advantage of interleukin-3-dependent 32Dcl3 hematopoietic precursor cells which, in addition to undergoing granulocytic differentiation in response to granulocyte colony-stimulating factor, were found to be induced for limited proliferation, but not differentiation, by granulocyte-macrophage colony-stimulating factor. It was shown that ectopic expression of Egr-1 blocked granulocyte colony-stimulating factor-induced terminal granulocytic differentiation, consistent with previous findings. In addition, ectopic expression of Egr-1 endowed 32Dcl3 cells with ability to be induced by granulocyte-macrophage colony-stimulating factor for terminal differentiation exclusively along the macrophage lineage. Thus, evidence that Egr-1 potentiates terminal macrophage differentiation has been obtained, suggesting that Egr-1 plays a deterministic role in governing the development of hematopoietic cells along the macrophage lineage.

Animals↗
PubMed1994

Differentiation primary response genes and proto-oncogenes as positive and negative regulators of terminal hematopoietic cell differentiation.

By genetically manipulating hematopoietic cells of the myeloid lineage, including both normal cells and differentiation inducible leukemic cell lines, evidence was obtained to indicate that myeloid differentiation primary response (MyD) genes and proto-oncogenes, which are known to control cell growth, function as positive and negative regulators of terminal hematopoietic cell differentiation, which is associated with inhibition of cell growth, and, ultimately programmed cell death (apoptosis). Interferon regulatory factor-1 (IRF-1), an MyD gene induced by Interleukin 6 (IL-6) or Leukemia Inhibitory factor (LIF), plays a role in growth inhibition associated with terminal differentiation. Leucine zipper transcription factors of the fos/jun family, also identified as MyD genes, function as positive regulators of hematopoietic cell differentiation, increasing the propensity of myeloblastic leukemia cells to be induced for differentiation in vitro, and reducing the aggressiveness of their leukemic phenotype in vivo. The zinc finger transcription factor EGR-1, an MyD gene specifically induced upon macrophage differentiation, was shown to be essential for and to restrict differentiation along the macrophage lineage. Finally, evidence has been accumulating to indicate that the novel MyD genes--MyD116, MyD118 and gadd45 (a member in the MyD118 gene family)--play a role in growth arrest and apoptosis of hematopoietic cells, as well as other cell types. The proto-oncogenes c-myc and c-myb, known to regulate cellular growth, were shown to function as negative regulators of terminal differentiation. Both c-myc and c-myb are normally expressed in proliferating myeloblasts and suppressed following induction of differentiation. Deregulated and continuous expression of c-myc was shown to block terminal myeloid differentiation at an intermediate stage in the progression from immature blasts to mature macrophages, whereas deregulated and continuous expression of c-myb blocked the terminal differentiation program at the immature myeloblast stage. By manipulating myc function in conditional (differentiation inducible) mutant myeloblastic leukemia cell lines, expressing a chimeric mycer transgene, it was shown that there is a window during myeloid differentiation, after the addition of the differentiation inducer, when the terminal differentiation program switches from being dependent on c-myc suppression to becoming c-myc suppression independent, and where activation of c-myc has no apparent effect on mature macrophages. These myeloblastic leukemia cell lines provide a powerful tool to increase our understanding of the role of c-myc in normal hematopoiesis and in leukemogenesis, while also providing a strategy to clone myc target genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptor Proteins, Signal Transducing↗
PubMed1994

The novel primary response gene MyD118 and the proto-oncogenes myb, myc, and bcl-2 modulate transforming growth factor beta 1-induced apoptosis of myeloid leukemia cells.

Cell numbers are regulated by a balance among proliferation, growth arrest, and programmed cell death. A profound example of cell homeostasis, controlled throughout life, is the complex process of blood cell development, yet little is understood about the intracellular mechanisms that regulate blood cell growth arrest and programmed cell death. In this work, using transforming growth factor beta 1 (TGF beta 1)-treated M1 myeloid leukemia cells and genetically engineered M1 cell variants, the regulation of growth arrest and apoptosis was dissected. Blocking of early expression of MyD118, a novel differentiation primary response gene also shown to be a primary response gene induced by TGF beta 1, delayed TGF beta 1-induced apoptosis, demonstrating that MyD118 is a positive modulator of TGF beta 1-mediated cell death. Elevated expression of bcl-2 blocked the TGF beta 1-induced apoptotic pathway but not growth arrest induced by TGF beta 1. Deregulated expression of either c-myc or c-myb inhibited growth arrest and accelerated apoptosis, demonstrating for the first time that c-myb plays a role in regulating apoptosis. In all cases, the apoptotic response was correlated with the level of MyD118 expression. Taken together, these findings demonstrate that the primary response gene MyD118 and the c-myc, c-myb, and bcl-2 proto-oncogenes interact to modulate growth arrest and apoptosis of myeloid cells.

Animals↗
PubMed1994

The gadd and MyD genes define a novel set of mammalian genes encoding acidic proteins that synergistically suppress cell growth.

A remarkable overlap was observed between the gadd genes, a group of often coordinately expressed genes that are induced by genotoxic stress and certain other growth arrest signals, and the MyD genes, a set of myeloid differentiation primary response genes. The MyD116 gene was found to be the murine homolog of the hamster gadd34 gene, whereas MyD118 and gadd45 were found to represent two separate but closely related genes. Furthermore, gadd34/MyD116, gadd45, MyD118, and gadd153 encode acidic proteins with very similar and unusual charge characteristics; both this property and a similar pattern of induction are shared with mdm2, whic, like gadd45, has been shown previously to be regulated by the tumor suppressor p53. Expression analysis revealed that they are distinguished from other growth arrest genes in that they are DNA damage inducible and suggest a role for these genes in growth arrest and apoptosis either coupled with or uncoupled from terminal differentiation. Evidence is also presented for coordinate induction in vivo by stress. The use of a short-term transfection assay, in which expression vectors for one or a combination of these gadd/MyD genes were transfected with a selectable marker into several different human tumor cell lines, provided direct evidence for the growth-inhibitory functions of the products of these genes and their ability to synergistically suppress growth. Taken together, these observations indicate that these genes define a novel class of mammalian genes encoding acidic proteins involved in the control of cellular growth.

3T3 Cells↗
PubMed1994

Induction of p21 (WAF-1/CIP1) during differentiation.

The recently cloned protein, p21 (WAF1/CIP1) is a downstream effector of p53, and mediates growth arrest by inhibiting the action of G1 cyclin-dependent kinases. Since cellular differentiation is frequently characterized by G1 arrest, we examined whether p21 upregulation occurs in differentiation. We show that p21 expression is triggered by multiple differentiation-inducing agents in hematopoietic and hepatoma cells through a p53-independent pathway. The dramatic rise in p21 levels occurs as an immediate early response to differentiation inducers. The induction of p21 is coupled to the expression of early differentiation markers, and is uncoupled from apoptosis. Finally, evidence is presented that p21 expression is uncoupled from G1 arrest in the presence of deregulated c-myc.

Apoptosis↗