DNMT and HDAC inhibitors modulate MMP-9-dependent H3\xa0N-terminal tail proteolysis and osteoclastogenesis

Yonghwan Shin,Kyungpyo Park,Woojin An,Byoungsan Moon,Nikhil B Ghate,Wange Lu

doi:10.1186/s13072-019-0270-0

Yonghwan Shin, Kyungpyo Park + Show 4 more

Open Access

https://doi.org/10.1186/s13072-019-0270-0

Copy DOI

Abstract

BackgroundMMP-9-dependent proteolysis of histone H3 N-terminal tail (H3NT) is an important mechanism for activation of gene expression during osteoclast differentiation. Like other enzymes targeting their substrates within chromatin structure, MMP-9 enzymatic activity toward H3NT is tightly controlled by histone modifications such as H3K18 acetylation (H3K18ac) and H3K27 monomethylation (H3K27me1). Growing evidence indicates that DNA methylation is another epigenetic mechanism controlling osteoclastogenesis, but whether DNA methylation is also critical for regulating MMP-9-dependent H3NT proteolysis and gene expression remains unknown.ResultsWe show here that treating RANKL-induced osteoclast progenitor (OCP) cells with the DNMT inhibitor 5-Aza-2′-deoxycytidine (5-Aza-CdR) induces CpG island hypomethylation and facilitates MMP-9 transcription. This increase in MMP-9 expression results in a significant enhancement of H3NT proteolysis and OCP cell differentiation. On the other hand, despite an increase in levels of H3K18ac, treatment with the HDAC inhibitor trichostatin A (TSA) leads to impairment of osteoclastogenic gene expression. Mechanistically, TSA treatment of OCP-induced cells stimulates H3K27ac with accompanying reduction in H3K27me1, which is a key modification to facilitate stable interaction of MMP-9 with nucleosomes for H3NT proteolysis. Moreover, hypomethylated osteoclastogenic genes in 5-Aza-CdR-treated cells remain transcriptionally inactive after TSA treatment, because H3K27 is highly acetylated and cannot be modified by G9a.ConclusionsThese findings clearly indicate that DNA methylation and histone modification are important mechanisms in regulating osteoclastogenic gene expression and that their inhibitors can be used as potential therapeutic tools for treating bone disorders.

Highlights

matrix metalloproteinases (MMPs)-9-dependent proteolysis of histone H3 N-terminal tail (H3NT) is an important mechanism for activation of gene expression during osteoclast differentiation
We demonstrated that the DNA methyltransferase (DNMT) inhibitor 5-Aza-CdR significantly facilitated RANKL-induced osteoclast precursor (OCP) cell differentiation through CpG demethylation and transcriptional activation of matrix metalloproteinase 9 (MMP-9) gene
The current study supports this hypothesis by showing that treatment of OCP-induced cells with the DNMT inhibitor 5-Aza-CdR stimulates MMP-9-dependent H3NT proteolysis and augments the expression of a group of genes, whose products are critical for the formation of multinucleated osteoclasts and their bone-resorbing activities

Summary

Introduction

MMP-9-dependent proteolysis of histone H3 N-terminal tail (H3NT) is an important mechanism for activation of gene expression during osteoclast differentiation. It has become clear that epigenetic alterations are important in controlling osteoclastogenic gene transcription as well as driving osteoclast formation and activity [13, 14] These epigenetic changes include DNA methylation at CpG dinucleotides and posttranslational modifications of histone tails [15,16,17,18,19,20]. Since abrogation of H3NT proteolysis by MMP-9 shRNA and inhibitors resulted in defective osteoclastogenesis under RANKL treatment conditions, the role for MMP-9-dependent H3NT proteolysis in osteoclast differentiation was firmly established [21] Beyond these initial works, our follow-up experiments showed that MMP-9 enzymatic activity toward nucleosomal H3NTs is dependent on p300-mediated H3K18ac and G9a-mediated H3K27me, establishing important osteoclastogenic functions for p300 and G9a [22]

Methods

Results

Discussion

Conclusion