MicroRNA-322 (miR-322) and Its Target Protein Tob2 Modulate Osterix (Osx) mRNA Stability

• Published in: The Journal of biological chemistry 2013-05, Vol.288 (20), p.14264-14275
• Main Authors: Gámez, Beatriz, Rodríguez-Carballo, Edgardo, Bartrons, Ramon, Rosa, José Luis, Ventura, Francesc
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Animals; Base Sequence; Bone; Bone Morphogenetic Protein (BMP); Cell Cycle Proteins - metabolism; Cell Differentiation; Cell Line; Cell Proliferation; Gene Expression Profiling; Gene Expression Regulation; Gene Regulation; HeLa Cells; Humans; Mice; MicroRNA; MicroRNAs - genetics; MicroRNAs - metabolism; MicroRNAs - physiology; Molecular Sequence Data; mRNA Decay; mRNA Degradation; Osteoblast Differentiation; Osteoblasts; Osteoblasts - cytology; Osteogenesis - physiology; Osterix; Polyadenylation; RNA Stability; RNA, Messenger - metabolism; Sequence Homology, Nucleic Acid; Sp7 Transcription Factor; Tob2; Transcription Factors - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.432104

Osteogenesis depends on a coordinated network of signals and transcription factors such as Runx2 and Osterix. Recent evidence indicates that microRNAs (miRNAs) act as important post-transcriptional regulators in a large number of processes, including osteoblast differentiation. In this study, we performed miRNA expression profiling and identified miR-322, a BMP-2-down-regulated miRNA, as a regulator of osteoblast differentiation. We report miR-322 gain- and loss-of-function experiments in C2C12 and MC3T3-E1 cells and primary cultures of murine bone marrow-derived mesenchymal stem cells. We demonstrate that overexpression of miR-322 enhances BMP-2 response, increasing the expression of Osx and other osteogenic genes. Furthermore, we identify Tob2 as a target of miR-322, and we characterize the specific Tob2 3′-UTR sequence bound by miR-322 by reporter assays. We demonstrate that Tob2 is a negative regulator of osteogenesis that binds and mediates degradation of Osx mRNA. Our results demonstrate a new molecular mechanism controlling osteogenesis through the specific miR-322/Tob2 regulation of specific target mRNAs. This regulatory circuit provides a clear example of a complex miRNA-transcription factor network for fine-tuning the osteoblast differentiation program. Background: miRNAs exert important roles during osteoblast proliferation and differentiation. Results: miR-322 induces expression of osteogenic genes by down-regulation of expression of Tob2, which binds to the 3′-UTR of Osx and modulates its degradation. Conclusion: miR-322 and its target Tob2 are regulators of osteogenesis through control of Osx mRNA degradation. Significance: We have identified a miRNA-transcription factor network that allows fine-tuning of the osteoblast differentiation program.