Inducer-mediated commitment of murine erythroleukemia cells to differentiation: a multistep process.

Abstract

There are a number ofagents which, when added to cultures of murine erythroleukemia cells (MELC), markedly increase the probability of commitment to express the characteristics of terminal erythroid differentiation, including loss of proliferative capacity and increased accumulation of globin mRNA and hemoglobin. Some characteristics of inducer-mediated commitment of MELC to terminal erythroid differentiation were examined by determining the effects of dexamethasone (an inhibitor of inducer-mediated MELC differentiation) and of hemin (an inducer of globin mRNA accumulation). Previously, it was shown that exposure of MELC to hexamethylene-bisacetamide (HMBA) leads to commitment, detectable within 12 hr. MELC cultured with both HMBA and dexamethasone do not express commitment. MELC transferred from culture with HMBA and dexamethasone to cloning medium without these agents express commitment to terminal erythroid differentiation, indicating that MELC retain a "memory" for some early HMBA-mediated changes leading to commitment which occur even in the presence of the inhibitory steroid. The kinetics of commitment in experiments in which exposure to HMBA is interrupted, or dexamethasone is added to the culture with HMBA, suggest that there is a rate-limiting step early in the commitment process. The memory for this step persists for more than one cell cycle. Addition ofhemin to cultures with HMBA and dexamethasone initiates accumulation of globin mRNA but does not reverse the steroid-mediated inhibition of terminal cell division (that is, the cells retain their proliferative capacity). Inducer-mediated MELC commitment is associated with accumu-

Induction by HMBA and DMSO of genes introduced into mouse erythroleukemia and other cell lines by transient transfection.

“…A property of endogenous mouse globin gene induction is that it shows eventual commitment or inducer independence (Gusella et al 1976;Chen et al 1982). No data are available to determine whether the same is true of stably integrated inducible genes, but the transient response does not show this property.…”

“…In addition, cellular DNA undergoes a cyclical change in cytosine methylation (Razin et al 19881. These early events occur at a time when the differentiation process requires the continued presence of inducer, but after 8-12 hr, the cells reach a committed state, in which terminal differentiation continues, and the mouse globin genes are expressed in the absence of inducer {Gusella et al 1976;Chen et al 1982).…”

c-Jun inhibits NF-E2 transcriptional activity in association with p18/maf in Friend erythroleukemia cells

“…When exposed to DMSO or other inducers, F-MEL cells undergo phenotypic changes that resemble the ®nal stages of normal erythropoiesis (Friend et al, 1971;Chen et al, 1982). The most striking feature is the increased synthesis of globin chains which results primarily from the activation of globin gene transcription (Charnay et al, 1984;Profous-Juchelka et al, 1983).…”

Enhancement of antitumor activity of herpes simplex virus γ134.5-deficient mutant for oral squamous cell carcinoma cells by hexamethylene bisacetamide

“…31,32 When mock-infected cells were treated with 5 mM HMBA for 24 h, flat cells and elongated cells appeared (Figure 1a and b). For viral infection, cells were infected with HSV-1 at an appropriate MOI and cultured at 371C after an adsorption period of 1 h. In FI cells infected with R849 at an MOI of 2 and cultured for 24 h, a proportion of cells became rounded, and multinucleated cells with vacuoles were observed ( Figure 1c).…”