Cell-cycle–dependent oscillation of GATA2 expression in hematopoietic cells

Abstract

In vitro manipulation of hematopoietic stem cells (HSCs) is a key issue in both transplantation therapy and regenerative medicine, and thus new methods are required to achieve HSC expansion with self-renewal. GATA2 is a transcription factor controlling pool size of HSCs. Of interest, continuous overexpression of GATA2 does not induce HSC proliferation. In this report, we demonstrate that GATA2 expression, in leukemic and normal hematopoietic cells, oscillates during the cell cycle, such that expression is high in S phase but low in G 1 /S and M phase.GATA2 binding to target Bcl-X gene also oscillates in accordance with GATA2 expression. Using a green fluorescent protein (GFP)-GATA2 fusion protein, we demonstrate cell-cycle-specific activity of proteasome-dependent degradation of GATA2. Immunoprecipitation/immunoblotting analysis demonstrated phosphorylation of GATA2 at cyclin-dependent kinase (Cdk)-consensus motifs, S/T 0 P ؉1 , and interaction of GATA2 with Cdk2/ cyclin A2-, Cdk2/cyclin A2-, and Cdk4/ cyclin D1-phosphorylated GATA2 in vitro. Mutants in phosphorylation motifs exhibited altered expression profiles of GFP-GATA2 domain fusion proteins. These results indicate that GATA2 phosphorylation by Cdk/cyclin systems is responsible for the cell-cycle-dependent regulation of GATA2 expression, and suggest the possibility that a cell-cycle-specific "onoff" response of GATA2 expression may control hematopoietic-cell proliferation and survival. IntroductionHematopoietic stem cells (HSCs) give rise to the immunohematopoietic system throughout the lifetime of host animals. 1 HSCs have distinctive systems regulating their proliferation and differentiation. These systems maintain steady-state hematopoiesis, and respond to stresses, including infection, hypoxia, and blood loss. 1,2 Two types of cell division occur in HSCs: one type produces differentiated daughter cells to supply mature blood cells, while the other type reproduces HSCs (self-renewal division) to maintain life-long hematopoiesis. 1,2 Of interest, in the bone marrow reservoir of HSCs, more than 70% of bone marrow HSCs are quiescent (G 0 phase), maintaining high proliferative capacity and pluripotency. 3 In contrast, their quiescent mature progeny generally lack the capacity for growth and division.Directing the expansion of HSCs in vitro is an urgent problem that must be solved to meet the needs of transplantation therapy and to fulfill the promise of regenerative medicine. 4 HSC self-renewal and maturation divisions appear to be controlled, at least in part, by transcription factors (MEL/ELF4, 5 Gfi1 6,7 ), and also by cellcycle regulatory factors (cyclin-dependent kinase (Cdk) inhibitor, p21 Cip1/Waf1 , 8 p18 INK4C 9 phosphatase and tensin homologue (PTEN), 10 c-Myc, 11 and Myc antagonist, Mad 1 12 ). Analysis of mice deficient in Gfi1, 6,7 p21 Cip1/Waf1 , 8 or PTEN 10 revealed increased marrow HSC cycling and subsequent exhaustion of HSCs, and suggest possible cooperation between transcription factors and cell-cycle regulators.GATA2 is a member of th...

Regulation of GATA-binding Protein 2 Levels via Ubiquitin-dependent Degradation by Fbw7

“…Therefore, it is important to clarify the molecular mechanisms involved in the control of GATA2 levels. Although cellular GATA2 levels are regulated by transcriptional control and proteasome-mediated degradation (37,38), ubiquitin E3 ligase, which ubiquitylates GATA2 to promote degradation via the ubiquitin-proteasome system, has not been identified. In the present study, we demonstrated that GATA2 is a novel CPD-dependent substrate for Fbw7.…”

GATA2 regulates differentiation of bone marrow-derived mesenchymal stem cells

“…GATA2 expression oscillates during the cell cycle such that expression is high in the S phase but low in G1/S and M phases. 32 Moreover,…”

“…Previous studies of hematopoietic cells have suggested that GATA2 expression varies during the cell cycle and that GATA2 regulates cell-cycle regulators. 32,33 We, therefore, evaluated whether the cell cycle was altered in BM-MSC in which GATA2 expression was inhibited. The number of cells present in G1/G0 was significantly increased when GATA2 expression was decreased (Figure 4), which was due to the significantly increased proportion of cells in the G1 phase (Online Supplementary Figure S4).…”

Dynamic Stabilization in the PU1-GATA1 Circuit Using a Model with Time-Dependent Kinetic Change

“…Activity-level fluctuations are also theorized to play important roles in protein and gene regulation and adaptation (Day 2009;Gerland and Hwa 2009;Henzler-Wildman and Kern 2007). In addition to stochastic fluctuations, GATA1 levels are known to oscillate in response to the cell cycle, and it is well-known that oscillatory behavior is exhibited in a wide range of biomolecular systems (Koga et al 2007;Goldbeter 1996). In fact, the hematopoietic stem cell activity is linked to the biological rhythms of the circadian cycle (Mendez-Ferrer et al 2008).…”