Arginine Methylation Provides Epigenetic Transcription Memory for Retinoid-Induced Differentiation in Myeloid Cells

Abstract

Cellular differentiation is governed by changes in gene expression, but at the same time, a cell's identity needs to be maintained through multiple cell divisions during maturation. In myeloid cell lines, retinoids induce gene expression and a well-characterized two-step lineage-specific differentiation. To identify mechanisms that contribute to cellular transcriptional memory, we analyzed the epigenetic changes taking place on regulatory regions of tissue transglutaminase, a gene whose expression is tightly linked to retinoid-induced differentiation. Here we report that the induction of an intermediary or "primed" state of myeloid differentiation is associated with increased H4 arginine 3 and decreased H3 lysine 4 methylation. These modifications occur before transcription and appear to prime the chromatin for subsequent hormone-regulated transcription. Moreover, inhibition of methyltransferase activity, preacetylation, or activation of the enzyme PAD4 attenuated retinoid-regulated gene expression, while overexpression of PRMT1, a methyltransferase, enhanced retinoid responsiveness. Taken together, our results suggest that H4 arginine 3 methylation is a bona fide positive epigenetic marker and regulator of transcriptional responsiveness as well as a signal integration mechanism during cell differentiation and, as such, may provide epigenetic memory.The HL-60 cell line is a well-characterized M2 myeloid leukemia cell line (6) that can be induced to undergo differentiation along different pathways, myeloid versus monocytic, in response to a variety of physiological and pharmacological stimuli. The process of myeloid differentiation itself involves two distinct and sequential steps. The first is an identifiable intermediate state termed the precommitment or primed state, and the second is a series of late events that lead to the onset of lineage-specific terminal differentiation (55-58). Primed cells are characterized by altered nuclear structure and feature retention of phenotype, a form of cellular memory that can last for several cell cycles. Most significantly, primed cells require only an abbreviated exposure to an appropriate inducer, such as all-trans-retinoic acid, for onset of G 1 / 0 -specific growth arrest and phenotypic differentiation (55). For example, a short exposure (16 to 24 h) to dimethyl sulfoxide (DMSO) or vitamin D induces a state of precommitment in HL-60 cells. Subsequent exposure of these precommitted cells to another inducer, such as all-trans-retinoic acid, results in the onset of growth arrest and differentiation that is much more rapid (Ͻ24 h) than for cells that have not been subject to precommitment (Ͼ48 h). In this example, DMSO exposure results in the acquisition of a precommitment memory, a state which can be sustained for more than one cell cycle (55). These experimental observations have been explained by suggesting a two-step model for induction of terminal differentiation in the cells. In this model, early events preceding precommitment regulate growth arrest, and late events ...

Epigenetic regulation of normal and malignant hematopoiesis

“…The role of PRMTs in hematopoiesis, specifically in myeloid differentiation, was highlighted by Balint et al (2005a, b), who demonstrated the methylation of H4R3 'primes', the regulatory region of specific genes for RAinduced myeloid differentiation (Balint et al, 2005b). Treatment of HL60 myeloid leukemia cells with vitamin D or dimethyl sulfoxide induced a 'precommitment' state that was linked to a rapid decrease in promoter H3K4 methylation and an increase in enhancer H4R3 methylation of the tissue transglutaminase gene, whose expression is linked to RA-induced differentiation.…”

“…Treatment of HL60 myeloid leukemia cells with vitamin D or dimethyl sulfoxide induced a 'precommitment' state that was linked to a rapid decrease in promoter H3K4 methylation and an increase in enhancer H4R3 methylation of the tissue transglutaminase gene, whose expression is linked to RA-induced differentiation. These 'primed' cells were then treated with RA, resulting in H4 acetylation and H3K4 methylation and transcriptional activation (Balint et al, 2005b). Also implicated in this chain of events is the enzyme peptidyl arginine deiminase, PAD4, which removes the methyl mark on H4R3, and is also associated with RA-induced gene activation .…”

Regulation of the Nuclear Poly(A)-binding Protein by Arginine Methylation in Fission Yeast

“…Accordingly, extensive large scale efforts have aimed to identify arginine methylated proteins (23)(24)(25). Based on these and other studies, arginine methylation appears to impact a variety of cellular processes including ribosome biosynthesis (26), T-cell activation (27), cytokine and interferon signaling (28), cell differentiation (29), and DNA repair (30). The role of arginine methylation in these cellular pathways is likely regulated by biochemical activities such as protein-protein interactions (31,32), protein subcellular localization (33,34), transcription and chromatin remodeling (35,36), mRNA metabolism (37,38), and translation (26,39).…”

PRMT1-mediated arginine methylation of PIAS1 regulates STAT1 signaling

“…Therefore, we established transient overexpression of wild-type PRMT1 (WT) and the catalytically inactive PRMT1 mutant XGX (Balint et al 2005), which were equally well expressed (Fig. 4A).…”

“…The following plasmids were used: pcDNA3.1-PRMT1 wild-type and pcDNA3.1-PRMT1-Myc XGX mutant were published recently (Balint et al 2005). pGex2T-GAR and pGex2T-PRMT3 were described previously (Tang et al 1998).…”