Nuclear transition protein TNP1 is a crucial player mediating histone-protamine exchange in condensing spermatids. A unique combination of intrinsic disorder and multivalent properties turns TNP1 into an ideal agent for orchestrating the formation of versatile TNP-DNA assembly and endows the protein with potent value for vaccine design. Despite its significance, the physicochemical property and the molecular mechanism taken by TNP1 for histone replacement and DNA condensation are still poorly understood. In this study, for the first time, we expressed and purified in vitro human TNP1. We investigated the hierarchical dynamics of TNP1: DNA interaction by combing computational simulations, biochemical assay, fluorescence imaging, and atomic force microscopy. We analyzed fuzzy interactions between TNP1 and DNA at the atomistic level and assessed the influence of TNP1 association on the electrostatic and mechanical properties of DNA. Furthermore, the alteration of the physicochemical properties of the TNP1-DNA complex modulates its molecular assembly and phase separation. Our study sets the foundation for understanding TNP1-mediated histone-protamine replacement and sheds light on the encapsulation of genetic material by TNP1 for vaccine development.
STING (stimulator of interferon genes) is a crucial protein in the innate immune system's response to viral and bacterial infections. In this study, we investigated the mechanistic and energetic mechanism of the conformational transition process of STING activated by cGAMP binding. We found that the STING connector region undergoes an energetically unfavorable transition during this process, which is compensated by the favorable interaction between cGAMP and the STING ligand binding domain. We utilized enhanced sampling methods to study STING's rotation and finds that several disease-causing mutations, such as N154S and V155L, can result in a smoother transition process, while V147L exhibits unfavorable conformational transition energy. These findings indicate that V147L may not be a gain-of-function mutation, as previously thought, and are further supported by an evolutionary analysis of the STING connector region. Overall, our study provides detailed insights into the mechanism of STING's rotation and has implications for the development of treatments for STING-related diseases.
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