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Serine phosphorylation of RUNX2 with novel potential functions as negative regulatory mechanisms
Hee-Jun Wee1, Gang Huang, Katsuya Shigesada
1Department of Viral Oncology, Kyoto University, Japan.
Abstract:
The RUNX family represents a small group of heterodimeric transcription factors that master-regulate osteogenesis and hematopoiesis in mammals. Their genetic defects cause human diseases such as cleidocranial dysplasia (CCD) and acute myelogenous leukemia. However, the mechanism(s) regulating their functions are still poorly understood. Here, we report a novel observation that suggests that the osteogenesis-associated homologue RUNX2 is negatively regulated by the phosphorylation of two conserved serines (S104 and S451) in two distinct functional aspects. The phosphorylation of S104 could abolish the heterodimerization of RUNX2 with the partner subunit, PEBP2beta, which enhances the metabolic stability of RUNX2. On the other hand, the phosphorylation of S451 resides within the C-terminal transcription inhibition domain of RUNX2 and hence is implicated in its functional mobilization. One CCD mutation, S104R of RUNX2, appears to mimic the phosphorylation-dependent inhibition of heterodimerization, thereby rendering RUNX2 metabolically unstable.
Insights
RUNX2, a key transcription factor for bone formation, is regulated by phosphorylation. Phosphorylation of RUNX2 at S104 and S451 affects its stability and function, impacting diseases like cleidocranial dysplasia.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The RUNX family of transcription factors are critical regulators of osteogenesis and hematopoiesis.
- Dysregulation of RUNX factors is linked to human diseases including cleidocranial dysplasia (CCD) and acute myelogenous leukemia.
- Mechanisms controlling RUNX factor function remain incompletely understood.
Purpose of the Study:
- To investigate the regulatory mechanisms governing the function of RUNX2, an osteogenesis-associated homologue.
- To identify specific phosphorylation sites on RUNX2 and their impact on its biological activity.
Main Methods:
- The study focused on analyzing the effects of phosphorylation on RUNX2 function.
- Investigated the role of specific serine residues (S104 and S451) in RUNX2 regulation.
- Examined the impact of a CCD mutation (S104R) on RUNX2 stability and function.
Main Results:
- RUNX2 function is negatively regulated by the phosphorylation of two conserved serines: S104 and S451.
- Phosphorylation of S104 disrupts RUNX2 heterodimerization with PEBP2beta, affecting its metabolic stability.
- Phosphorylation of S451, located in the C-terminal inhibitory domain, influences RUNX2's functional mobilization.
- The CCD mutation S104R mimics phosphorylation-dependent inhibition, leading to RUNX2 metabolic instability.
Conclusions:
- RUNX2 activity is modulated through phosphorylation at distinct serine residues.
- Phosphorylation of S104 and S451 plays crucial roles in regulating RUNX2 stability and transcriptional activity.
- Understanding these regulatory mechanisms provides insights into the pathogenesis of RUNX2-related disorders like CCD.