Histone deacetylase inhibitor MS-275 stimulates bone formation in part by enhancing Dhx36-mediated TNAP transcription

Abstract

Histone deacetylases (HDACs) deacetylate both histones and nonhistone proteins and play a key role in the regulation of physiologic and aberrant gene expression. Inhibition of HDACs has emerged as a promising therapeutic target for cancer and neurologic diseases. In this study we investigated the osteogenic effect and mechanism of action of MS-275, a class I HDAC inhibitor with preference for HDAC1. Both local and systemic administration of MS-275 stimulated bone regeneration in animal models. MS-275 stimulated mRNA expression and activity of the early osteogenic marker tissue-nonspecific alkaline phosphatase (TNAP) in bone tissue and osteogenic cells. By using a series of TNAP promoter deletion constructs and a DNA affinity precipitation assay, we identified DExH-box helicase Dhx36 as a factor that binds to the MS-275 response element in the TNAP promoter. We also found that Dhx36 binding to the MS-275 response element is crucial for MS-275 induction of TNAP transcription. Dhx36 physically interacted with a subset of HDACs (HDAC1 and -4) whose protein levels were downregulated by MS-275, and forced expression of these HDACs blunted the stimulatory effects of MS-275 by a deacetylase activity-independent mechanism(s). Taken together, the results of our study show that MS-275 induces TNAP transcription by decreasing the interaction of HDAC1/4 with Dhx36, which can at least in part contribute to the bone anabolic effects of MS-275.

Binding of G-quadruplexes to the N-terminal Recognition Domain of the RNA Helicase Associated with AU-rich Element (RHAU)

“…Although the structural and biophysical characterization of G-quadruplexes has progressed rapidly, the mechanistic basis for their recognition and remodeling is poorly understood. RHAU has emerged as a primary quadruplex resolvase in eukaryotic cells, and the functional consequences of quadruplex remodeling has been established in a small number of important processes (17,18,21,41,42). Therefore, our goal was to make biophysical inroads to the process by examining the recognition of G-quadruplexes by the N-terminal region of RHAU that contains the RSM, a required region for quadruplex recognition.…”

Histone Deacetylase Inhibition Promotes Osteoblast Maturation by Altering the Histone H4 Epigenome and Reduces Akt Phosphorylation

“…Moreover, there is a need to optimize bone tissue-engineering strategies for the treatment of non-union fractures and critical size defects. Numerous laboratories have reported that HDIs enhance osteoblast differentiation in vitro (11)(12)(13)(14)(15)(35)(36)(37). In this study, we characterized epigenetic events that occur in SAHA-treated osteoblasts to understand the pathways that control osteoblast differentiation.…”

Evidence That G-quadruplex DNA Accumulates in the Cytoplasm and Participates in Stress Granule Assembly in Response to Oxidative Stress

“…The fact that many cells can readily take up G4DNA indicates that this mechanism may also allow the cell to respond to its external environment as well as internal stress (67,72). Although our results suggest important roles for G4DNA in the regulation of cytoplasmic cellular processes, other studies have suggested roles for G4DNA in modulating transcription through the binding of helicases such as DHX36 (30,96,97), the RecQ family helicases (98,99), and the XPB and XPD helicases (75). It is possible that any G4DNA-binding protein may be regulated by freely diffusing G4DNA, leading to various cellular responses based on the large number of proteins that are reported to have G4DNA binding capacity (4, 100 -102).…”