Regulation of globin gene expression in human K562 cells by recombinant activin A

Abstract

Recent studies indicate that a purified protein, activin A, belongs to the transforming growth factor beta (TGF-beta) superfamily. Similar to TGF-beta, activin A can have different biologic activities, depending on the target tissues. We used recombinant activin A to demonstrate a possible regulatory role of this protein in modulating human erythroid differentiation in the human erythroid cell line, K562. Using genomic probes containing the second exon of alpha, beta, gamma, and epsilon globins, relative abundance of various types of globin transcripts in untreated and activin-treated K562 cells was examined with S1 nuclease analysis. Despite considerable homology amongst various globin sequences, these globin probes were highly specific for their unique mRNA species in the analyses. It was shown that the abundance of specific globin probe fragments for gamma and epsilon globins (209 nucleotides) as well as alpha (180 nucleotides), which were protected from S1 digestion, increased many fold in K562 cells treated with activin A. In contrast, there were no specific transcripts of beta globin detected in either the control or activin-treated cells. The increases in the level of fetal and embryonic beta-like and alpha globin transcripts also confirmed earlier studies of Northern and slot- blot analyses using globin cDNA as probes. In addition, nuclear run-off transcription assay using isolated nuclei indicated that most of the increase in the globin transcripts after activin treatment could be attributed to the stimulation of transcription rate for globin genes. Transient transfection assays also provide evidence that activin A significantly stimulated transcriptional activity of an epsilon globin promoter in K562, but not in the nonerythroid Chinese hamster ovary cells. Therefore, it was concluded that activin A exerts its effects on globin gene expression at the level of transcription in erythroid cells.

Activin A induces erythroid gene expressions and inhibits mitogenic cytokine‐mediated K562 colony formation by activating p38 MAPK

“…1A). These results are consistent with a previous report using Northern blot analysis [Frigon et al, 1992]. To examine the contribution of p38 MAPK and ERK, K562 cells were incubated in the presence or absence of p38 MAPK inhibitor (SB203580) or MEK/ERK inhibitor (PD98059) alone, or in combination with activin A for 3 days.…”

Truncated activin type II receptor inhibits erythroid differentiation in K562 cells

“…By contrast, in agreement with present findings, many studies had demonstrated that activin A can directly induce erythroleukemia cells into differentiation [Yu et al, 1987[Yu et al, , 1989Eto et al, 1987;Broxmeyer et al, 1988]. Incubation of purified erythroid progenitors and K562 cells with activin A was also found to lead to an increase in globin transcripts and hemoglobin accumulation [Frigon et al, 1992;Shao et al, 1992a]. Therefore, in addition to the indirect actions for promoting the proliferation of erythroid precursor cells, activin A may directly affect erythroid differentiation via interaction with receptors in the erythroid cells [Shao et al, 1992a;Yu et al, 1991].…”

Induced expression of the new cytokine, activin A, in human monocytes: inhibition by glucocorticoids and retinoic acid

“…4 Many studies have demonstrated that activin A can potentiate the proliferation and differentiation of erythroid progenitors in vitro [5][6][7][8] and induce human K562 to become haemoglobin-containing cells. 5,9 In addition, many in vivo studies in rats and mice [10][11][12] support the hypothesis that this protein may have erythropoietic enhancing activities. 5 It is conceivable that activin A molecules may also play a role(s) in the inflammatory response because inflammatory mediators, such as TNF-a, IL-1, interferon-g (IFN-g) and lipopolysaccharide (LPS), which are involved in host defence, also markedly enhance the production of activin A.…”