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Endocytosis plays a complex role in pathogen-host interactions. It serves as a pathway for pathogens to enter the host cell and acts as a part of the immune defense mechanism. Endocytosis involves the formation of lipid membrane vesicles and the reshaping of the cell membrane, a task predominantly managed by proteins containing BAR (Bin1/Amphiphysin/yeast RVS167) domains. Insights into how BAR domains can remodel and reshape cell membranes provide crucial information on infections and can aid the development of treatment. Aiming at deciphering the roles of the BAR dimers in lipid membrane bending and remodeling, we conducted extensive all-atom molecular dynamics simulations and discovered that the presence of helix kinks divides the BAR monomer into two segments—the “arm segment” and the “core segment”—which exhibit distinct movement patterns. Contrary to the prior hypothesis of BAR domains working as a rigid scaffold, we found that it functions in an “Arms-Hands” mode. These findings enhance the understanding of endocytosis, potentially advancing research on pathogen-host interactions and aiding in the identification of new treatment strategies targeting BAR domains. 

Introduction:The proteins of the Bin/Amphiphysin/Rvs167 (BAR) domain superfamily arebelieved to induce membrane curvature. PICK1 is a distinctive protein that consists of both a BAR anda PDZ domain, and it has been associated with numerous diseases. It is known to facilitate membranecurvature during receptor-mediated endocytosis. In addition to understanding how the BAR domainfacilitates membrane curvature, it's particularly interesting to unravel the hidden links between thestructural and mechanical properties of the PICK1 BAR domain. Methods:This paper employs steered molecular dynamics (SMD) to investigate the mechanical propertiesassociated with structural changes in the PICK1 BAR domains. Results:Our findings suggest that not only do helix kinks assist in generating curvature of BAR domains,but they may also provide the additional flexibility required to initiate the binding betweenBAR domains and the membrane Conclusion:We have observed a complex interaction network within the BAR monomer and at thebinding interface of the two BAR monomers. This network is crucial for maintaining the mechanicalproperties of the BAR dimer. Owing to this interaction network, the PICK1 BAR dimer exhibits differentresponses to external forces applied in opposite directions. 

Noncoding mutation hotspots have been identified in melanoma and many of them occur at the binding sites of E26 transformation-specific (ETS) proteins; however, their formation mechanism and functional impacts are not fully understood. Here, we used UV (Ultraviolet) damage sequencing data and analyzed cyclobutane pyrimidine dimer (CPD) formation, DNA repair, and CPD deamination in human cells at single-nucleotide resolution. Our data show prominent CPD hotspots immediately after UV irradiation at ETS binding sites, particularly at sites with a conserved TTCCGG motif, which correlate with mutation hotspots identified in cutaneous melanoma. Additionally, CPDs are repaired slower at ETS binding sites than in flanking DNA. Cytosine deamination in CPDs to uracil is suggested as an important step for UV mutagenesis. However, we found that CPD deamination is significantly suppressed at ETS binding sites, particularly for the CPD hotspot on the 5′ side of the ETS motif, arguing against a role for CPD deamination in promoting ETS-associated UV mutations. Finally, we analyzed a subset of frequently mutated promoters, including the ribosomal protein genesRPL13AandRPS20, and found that mutations in the ETS motif can significantly reduce the promoter activity. Thus, our data identify high UV damage and low repair, but not CPD deamination, as the main mechanism for ETS-associated mutations in melanoma and uncover important roles of often-overlooked mutation hotspots in perturbing gene transcription.