The circadian clock plays a critical role in regulating various physiological processes, including gene expression, metabolic regulation, immune response, and the sleep-wake cycle in living organisms. Post-translational modifications (PTMs) are crucial regulatory mechanisms to maintain the precise oscillation of the circadian clock. By modulating the stability, activity, cell localization and protein-protein interactions of core clock proteins, PTMs enable these proteins to respond dynamically to environmental and intracellular changes, thereby sustaining the periodic oscillations of the circadian clock. Different types of PTMs exert their effects through distincting molecular mechanisms, collectively ensuring the proper function of the circadian system. This review systematically summarized several major types of PTMs, including phosphorylation, acetylation, ubiquitination, SUMOylation and oxidative modification, and overviewed their roles in regulating the core clock proteins and the associated pathways, with the goals of providing a theoretical foundation for the deeper understanding of clock mechanisms and the treatment of diseases associated with circadian disruption.
Protein Processing, Post-Translational/physiology* ; Circadian Rhythm/physiology* ; Humans ; Animals ; CLOCK Proteins/physiology* ; Circadian Clocks/physiology* ; Phosphorylation ; Acetylation ; Ubiquitination ; Sumoylation

SIRT7, a sirtuin family member implicated in aging and disease, is a regulator of metabolism and stress responses. It remains elusive how human somatic stem cell populations might be impacted by SIRT7. Here, we found that SIRT7 expression declines during human mesenchymal stem cell (hMSC) aging and that SIRT7 deficiency accelerates senescence. Mechanistically, SIRT7 forms a complex with nuclear lamina proteins and heterochromatin proteins, thus maintaining the repressive state of heterochromatin at nuclear periphery. Accordingly, deficiency of SIRT7 results in loss of heterochromatin, de-repression of the LINE1 retrotransposon (LINE1), and activation of innate immune signaling via the cGAS-STING pathway. These aging-associated cellular defects were reversed by overexpression of heterochromatin proteins or treatment with a LINE1 targeted reverse-transcriptase inhibitor. Together, these findings highlight how SIRT7 safeguards chromatin architecture to control innate immune regulation and ensure geroprotection during stem cell aging.

OBJECTIVETo investigate the clinicopathologic features of calcium pyrophosphate dihydrate crystal deposition disease (CPPD-CDD).

METHODSThe clinical and pathologic profiles were retrospectively analysed in 20 cases of CPPD-CDD.

RESULTSCPPD-CDD was far more common in women, most frequently involving joints, especially the knees and presenting with various arthrisis. Abnormally calcified and the articular damages were characteristic features by imageing. Histologically, multifocal indigo granular calcinosis was seen in synovium and sometimes appeared as needle-shaped or rhomboid crystals, which characterized the CPPD.

CONCLUSIONSThough clinical symptoms of CPPD are quite variable, the definite diagnosis can be made by the abnormal calcification and joint damage radiographically and the indigo CPPD crystals histopathologically.

Adult ; Aged ; Aged, 80 and over ; Chondrocalcinosis ; diagnostic imaging ; pathology ; surgery ; Female ; Follow-Up Studies ; Hip Joint ; diagnostic imaging ; pathology ; surgery ; Humans ; Intervertebral Disc ; diagnostic imaging ; pathology ; surgery ; Knee Joint ; diagnostic imaging ; pathology ; surgery ; Magnetic Resonance Imaging ; Male ; Middle Aged ; Retrospective Studies ; Spinal Diseases ; diagnostic imaging ; pathology ; surgery ; Synovial Membrane ; pathology ; Tomography, X-Ray Computed