Dynamic Changes in Histone H3 Phosphoacetylation during Early Embryonic Stem Cell Differentiation Are Directly Mediated by Mitogen- and Stress-activated Protein Kinase 1 via Activation of MAPK Pathways

Abstract

Embryonic stem (ES) cells are pluripotent cells capable of unlimited self-renewal and differentiation into the three embryonic germ layers under appropriate conditions. Mechanisms for control of the early period of differentiation, involving exit from the pluripotent state and lineage commitment, are not well understood. An emerging concept is that epigenetic histone modifications may play a role during this early period. We have found that upon differentiation of mouse ES cells by removal of the cytokine leukemia inhibitory factor, there is a global increase in coupled histone H3 phosphorylation (Ser-10)-acetylation (Lys-14) (H3 phosphoacetylation). We show that this occurs through activation of both the extracellular signal-regulated kinase (ERK) and p38 MAPK signaling pathways. Early ES cell differentiation is delayed using pharmacological inhibitors of the ERK and p38 pathways. One common point of convergence of these pathways is the activation of the mitogen-and stress-activated protein kinase 1 (MSK1). We show here that MSK1 is the critical mediator of differentiation-induced H3 phosphoacetylation using both the chemical inhibitor H89 and RNA interference. Interestingly, inhibition of H3 phosphoacetylation also alters gene expression during early differentiation. These results point to an important role for both epigenetic histone modifications and kinase pathways in modulating early ES differentiation. Embryonic stem (ES)2 cells are pluripotent cells with the capacity for unlimited self-renewal or differentiation into the three germ layers: endoderm, ectoderm, and mesoderm. This ability to form different cell types under appropriate conditions makes them a powerful tool in the study of biological mechanisms and treatment of disease. Mouse ES cells are derived from the inner cell mass of the developing blastocyst (1). In vivo, the inner cell mass becomes organized into a pluripotent epithelial layer, the epiblast, from which embryonic tissues are derived (2). In vitro, mouse ES cells can be maintained in an undifferentiated state with the addition of the cytokine leukemia inhibitory factor (LIF) to culture media. LIF primarily acts via the JAK-STAT signaling pathway to maintain pluripotency (3). Self-renewal also is enhanced by inhibition of mitogen-activated protein kinase (MAPK) pathways (4). Withdrawal of LIF results in spontaneous differentiation of the ES cells into all three lineages, which is marked by changes in gene expression and cell morphology (see Fig. 1A).Although much focus has been placed on factors involved in self-renewal, the mechanisms regulating exit from the pluripotent state followed by commitment to specific lineages remain largely unknown. An emerging concept is that alterations in epigenetic histone modifications may be important during this timeframe (5). The nucleosome, with DNA wrapped around an octamer of core histones (H2A, H2B, H3, and H4), forms the basic building blocks of chromatin. Histone tails are subject to numerous covalent modifications, including acetylation, phosp...

Quercetin augments TRAIL-induced apoptotic death: Involvement of the ERK signal transduction pathway

“…It is well known that mitogen-and stress-activated kinase 1 (MSK1), a kinase downstream of ERK, plays an important role in modification of histone H3 [23,24]. We examined whether MSK1 is phosphorylated during treatment with quercetin.…”

MAP kinases and the control of nuclear events

“…Although consensus MAPK histone phosphorylation sites have not been described in vivo, MAPKs can activate histone-phosphorylating kinases (Cheung et al, 2000;Zhong et al, 2001). For example, ERK1/2 and p38a, -b can provoke changes in chromatin structure (Li et al, 2001;Illi et al, 2005;Schmeck et al, 2005) most likely owing to the activation of downstream kinases such as MSK1/2 (Saccani et al, 2002;Soloaga et al, 2003;Lee et al, 2006a;Vicent et al, 2006) or RSK2 (Cheung et al, 2000) that phosphorylate the N-terminal tail of histones. A surprising recent finding is that MAPKs bind to specific actively transcribed genes, as documented in yeast (Pokholok et al, 2006), reinforcing the idea that MAPKs participate actively in chromatin remodeling, perhaps explaining the observation that MAPKs such as p38a and ERK1/2 bind cellular DNA as judged by the use of chromatin immunoprecipitation assays in mammalian cells (Simone et al, 2004;Vicent et al, 2006).…”

SIRT1 deficiency compromises mouse embryonic stem cell hematopoietic differentiation, and embryonic and adult hematopoiesis in the mouse

“…31 When the Erk pathway is inhibited in LIF withdrawn cells, the pluripotent marker Oct4 shows delayed down-regulation. 31 SIRT1 inhibition reduces Erk1/2 signaling in cultured neurons, 32 so we assessed whether delay in loss of pluripotency markers in SIRT1 Ϫ/Ϫ EBs is associated with effects on the Erk pathway during SIRT1 Ϫ/Ϫ ESC commitment.…”

“…Phosphorylated Erk1/2 was gradually increased during early SIRT1 ϩ/ϩ ESC differentiation, consistent with a previous report. 31 However, Erk phosphorylation was greatly impaired in SIRT1 Ϫ/Ϫ cells ( Figure 5A-B). To evaluate signaling pathways for mesodermal differentiation within EBs, high-throughput mRNA expression profiling was used to examine gene expression involved in bone morphogenetic protein (BMP), FGF, and Wnt pathways.…”