PLAG1 and USF2 Co-regulate Expression of Musashi-2 in Human Hematopoietic Stem and Progenitor Cells

Abstract

SummaryMSI2, which is expressed predominantly in hematopoietic stem and progenitor cells (HSPCs), enforces HSPC expansion when overexpressed and is upregulated in myeloid leukemias, indicating its regulated transcription is critical to balanced self-renewal and leukemia restraint. Despite this, little is understood of the factors that enforce appropriate physiological levels of MSI2 in the blood system. Here, we define a promoter region that reports on endogenous expression of MSI2 and identify USF2 and PLAG1 as transcription factors whose promoter binding drives reporter activity. We show that these factors co-regulate, and are required for, efficient transactivation of endogenous MSI2. Coincident overexpression of USF2 and PLAG1 in primitive cord blood cells enhanced MSI2 transcription and yielded cellular phenotypes, including expansion of CD34+ cells in vitro, consistent with that achieved by direct MSI2 overexpression. Global chromatin immunoprecipitation sequencing analyses confirm a preferential co-binding of PLAG1 and USF2 at the promoter of MSI2, as well as regulatory regions corresponding to genes with roles in HSPC homeostasis. PLAG1 and USF2 cooperation is thus an important contributor to stem cell-specific expression of MSI2 and HSPC-specific transcriptional circuitry.

Plag1 regulates neuronal gene expression and neuronal differentiation of neocortical neural progenitor cells

“…and Msi2 (Belew et al, 2018;Voz et al, 2000), were not affected by Plag1 knockdown in neocortical NPCs (data not shown), which may suggest a cell type-or context-dependent function of Plag1. and Msi2 (Belew et al, 2018;Voz et al, 2000), were not affected by Plag1 knockdown in neocortical NPCs (data not shown), which may suggest a cell type-or context-dependent function of Plag1.…”

“…and Msi2 (Belew et al, 2018;Voz et al, 2000), were not affected by Plag1 knockdown in neocortical NPCs (data not shown), which may suggest a cell type-or context-dependent function of Plag1. However, as a recent ChIP-seq analysis for Plag1 in hematopoietic cells revealed a novel Plag1 binding motif containing the E-box consensus sequence (Belew et al, 2018), it is possible that genes without the conventional Plag1 motif are also directly targeted by Plag1. However, as a recent ChIP-seq analysis for Plag1 in hematopoietic cells revealed a novel Plag1 binding motif containing the E-box consensus sequence (Belew et al, 2018), it is possible that genes without the conventional Plag1 motif are also directly targeted by Plag1.…”

“…and Msi2 (Belew et al, 2018;Voz et al, 2000), were not affected by Plag1 knockdown in neocortical NPCs (data not shown), which may suggest a cell type-or context-dependent function of Plag1. The DEGs identified by Plag1 knockdown in our study include a substantial proportion with a conventional Plag1 binding motif (Meng et al, 2005;Voz et al, 2000).…”

“…Consistent with this function, Plag1 promotes cell proliferation (Declercq et al, 2005;Hensen, Valckenborgh, Kas, Ven, & Voz, 2002) and Plag1 mutant mice show pronounced growth retardation from the embryonic stage (Hensen et al, 2004), with this latter observation also implicating Plag1 in development. Plag1 is expressed in various fetal tissues including the brain, lung, liver and kidney (Alam, Zinyk, Ma, & Schuurmans, 2005;Kas et al, 1997), and it has been shown to regulate spermatogenesis and maintenance of hematopoietic stem and progenitor cells (Belew et al, 2018;Juma et al, 2017). Early-stage NPCs in the VZ of the developing mouse telencephalon express Plag1 (Alam et al, 2005), and mouse embryos with constitutive deletion of Plag1 were found to exhibit a thinner neocortex and premature neurogenesis compared with control embryos (Adnani et al, 2018).…”

“…Given its high level of expression in several fetal tissues (Kas et al, 1997), Plag1 may play similar roles in the regulation of other tissue stem cells, as it has been shown to do in hematopoietic stem-progenitor cells (Belew et al, 2018). Given its high level of expression in several fetal tissues (Kas et al, 1997), Plag1 may play similar roles in the regulation of other tissue stem cells, as it has been shown to do in hematopoietic stem-progenitor cells (Belew et al, 2018).…”