AUTHOR=Zhai Qiaoli , Zhao Yi , Wang Linping , Dai Yan , Zhao Peiqing , Xiang Xinxin , Liu Kui , Du Wenyan , Tian Wenxiu , Yang Baoye , Li Tao , Wang Lianqing TITLE=CircRNA hsa_circ_0008500 Acts as a miR-1301-3p Sponge to Promote Osteoblast Mineralization by Upregulating PADI4 JOURNAL=Frontiers in Cell and Developmental Biology VOLUME=8 YEAR=2020 URL=https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2020.602731 DOI=10.3389/fcell.2020.602731 ISSN=2296-634X ABSTRACT=

Circular RNAs (circRNAs) are regarded as pivotal regulators in bone metabolism. However, the role of circRNAs in osteoblast mineralization remains largely unknown. Herein, we explored the expression profiles of circRNAs in 4 groups of osteoblasts with varying mineralization processes. Hsa_circ_0008500 (circ8500), which is upregulated in the RNA-seq data, is sifted through 194 candidate circRNAs in osteoblasts during mineralization. We characterize the features of novel circRNAs and find that the elevated expression of circ8500 promotes osteoblast mineralization. Mechanistically, circ8500 contains a critical binding site for miR-1301-3p. We further show that circ8500 competitively binds miR-1301-3p to abolish its suppressive effect on peptidyl arginine deiminase 4 (PADI4). PADI4 works as a binding partner of RUNX2 and stabilizes its protein expression levels by inhibiting the ubiquitin-proteasome pathway. This work provides new insights on the circRNA patterns in osteoblasts and the role of PADI4 in matrix mineralization.