Mechanobiology plays a pivotal role in skeletal development and bone remodeling. Mechanical signals such as matrix stiffness, fluid shear stress, and hydrostatic pressure activate the Runt-related transcription factor 2 (RUNX2) bone-specific transcription factor through pathways including the mitogen-activated protein kinase (MAPK) signaling cascade and yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) effectors. RUNX2 itself affects chromatin remodeling and nuclear architecture via Lamin A/C and Nesprin 1, thereby directing osteogenic differentiation. Thus, RUNX2 acts both as a mechanosensor and mechanoregulator, whereas RUNX2’s mechanosensitivity has been leveraged as a target to achieve bone regeneration. Notably, post-translational modifications and epigenetic alterations can orchestrate this regulation, integrating metabolic and circadian signals. However, due to RUNX2’s nuclear localization, its targeting remains a challenging issue. To this end, indirect targeting, through mammalian/mechanistic target of rapamycin complex 1 (mTORC1) or microRNAs (miRNAs), offers new strategies to employ biomechanics in an attempt to intervene with bone diseases driven by mechanical cues or degeneration, and ultimately repair and regenerate the damaged tissues. Herein we critically elaborate upon molecular aspects of RUNX2 regulation towards exploitation at the clinical level.

The activator protein-1 (AP-1) transcription factor is a regulatory dimeric transcription factor complex, that responds to a wide range of intracellular and extracellular stimuli and controls gene expression involved in tumor initiation and progression. Comprised primarily of members of Jun and Fos protein subfamilies, AP-1 is activated downstream of major oncogenic signaling pathways such as the mitogen-activated protein kinase (MAPK) pathway and controls cellular processes including differentiation, invasion, proliferation and apoptosis. In various cancer types, AP-1 contributes to tumor growth by promoting tumor-like phenotypes and facilitating metastatic behavior. Furthermore, AP-1 can affect the tumor microenvironment by modulating inflammation and interaction with immune cells. AP-1 deregulation is linked to tumor heterogeneity and resistance to chemotherapy and radiation. Therefore, AP-1 has emerged as a potential therapeutic target. In preclinical models, direct and indirect targeting via upstream pathways of AP-1 components has demonstrated encouraging results. In addition, combinatorial approaches targeting AP-1 and other regulators may improve the effectiveness of treatment and overcome therapy resistance. In this review, we highlight the AP-1’s role as a critical hub in tumorigenesis that links oncogenic signaling to transcriptional regulation. We also focus on its regulation, function in the tumor microenvironment, and therapeutic potential in combating tumors.

Brain aging is characterized by extensive and dynamic epigenetic changes that reshape chromatin architecture and influence gene regulatory networks, leading to deregulation of transcriptional programs essential for neuronal survival, synaptic plasticity, and cognitive function. Emerging studies highlight the pivotal regulatory role of the Polycomb Repressive Complex 2 (PRC2) in brain aging, functioning mainly as an epigenetic silencer through the establishment of the H3K27me3 histone mark at gene promoters and enhancers, leading to transcriptional repression. Altered distribution and decreased activity of PRC2 during aging disrupts the balance between gene activation and repression, affecting pathways involved in neurogenesis, synaptic plasticity and stress response. Further interplay with other epigenetic regulators such as histone deacetylase 2 (HDAC2), DNA methyltransferases and non-coding RNAs forms an extensive network that contributes to cognitive decline, increasing vulnerability for neurodegeneration. In this review, we describe structural and functional aspects of PRC2, with emphasis on the potential of this epigenetic context-dependent regulator to integrate developmental, environmental and aging-related signals, to shape the transcriptional landscape of aging brain. We also discuss the newly developed PRC2-AgeIndex, which serves as a prognostic biomarker for age-related neurodegeneration and monitoring treatment response, as well as current PRC2-targeting options for healthy brain aging.