@article {69904, title = {Quantitative spatial analysis of chromatin biomolecular condensates using cryoelectron tomography.}, journal = {Proc Natl Acad Sci U S A}, volume = {122}, year = {2025}, month = {2025 May 13}, pages = {e2426449122}, abstract = {

Phase separation is an important mechanism to generate certain biomolecular condensates and organize the cell interior. Condensate formation and function remain incompletely understood due to difficulties in visualizing the condensate interior at high resolution. Here, we analyzed the structure of biochemically reconstituted chromatin condensates through cryoelectron tomography. We found that traditional blotting methods of sample preparation were inadequate, and high-pressure freezing plus focused ion beam milling was essential to maintain condensate integrity. To identify densely packed molecules within the condensate, we integrated deep learning-based segmentation with context-aware template matching. Our approaches were developed on chromatin condensates and were also effective on condensed regions of in situ native chromatin. Using these methods, we determined the average structure of nucleosomes to 6.1 and 12 {\r A} resolution in reconstituted and native systems, respectively, found that nucleosomes form heterogeneous interaction networks in both cases, and gained insight into the molecular origins of surface tension in chromatin condensates. Our methods should be applicable to biomolecular condensates containing large and distinctive components in both biochemical reconstitutions and certain cellular systems.

Preprint:\ https://www.biorxiv.org/content/10.1101/2024.12.01.626131v2

}, keywords = {Animals, Biomolecular Condensates, Chromatin, Cryoelectron Microscopy, Electron Microscope Tomography, Nucleosomes}, issn = {1091-6490}, doi = {10.1073/pnas.2426449122}, url = {https://doi.org/10.1073/pnas.2426449122}, author = {Zhou, Huabin and Hutchings, Joshua and Shiozaki, Momoko and Zhao, Xiaowei and Doolittle, Lynda K and Yang, Shixin and Yan, Rui and Jean, Nikki and Riggi, Margot and Yu, Zhiheng and Villa, Elizabeth and Rosen, Michael K} } @article {69688, title = {Quantitative Spatial Analysis of Chromatin Biomolecular Condensates using Cryo-Electron Tomography}, journal = {bioRxiv}, year = {2024}, month = {2024 Dec 02}, abstract = {

Phase separation is an important mechanism to generate certain biomolecular condensates and organize the cell interior. Condensate formation and function remain incompletely understood due to difficulties in visualizing the condensate interior at high resolution. Here we analyzed the structure of biochemically reconstituted chromatin condensates through cryo-electron tomography. We found that traditional blotting methods of sample preparation were inadequate, and high-pressure freezing plus focused ion beam milling was essential to maintain condensate integrity. To identify densely packed molecules within the condensate, we integrated deep learning-based segmentation with novel context-aware template matching. Our approaches were developed on chromatin condensates, and were also effective on condensed regions of in situ native chromatin. Using these methods, we determined the average structure of nucleosomes to 6.1 and 12 {\r A} resolution in reconstituted and native systems, respectively, and found that nucleosomes have a nearly random orientation distribution in both cases. Our methods should be applicable to diverse biochemically reconstituted biomolecular condensates and to some condensates in cells.

}, doi = {10.1101/2024.12.01.626131}, url = {https://doi.org/10.1101/2024.12.01.626131}, author = {Zhou, Huabin and Hutchings, Joshua and Shiozaki, Momoko and Zhao, Xiaowei and Doolittle, Lynda K. and Yang, Shixin and Yan, Rui and Jean, Nikki and Riggi, Margot and Yu, Zhiheng and Villa, Elizabeth and Rosen, Michael K.} } @article {68960, title = {Functionalization and higher-order organization of liposomes with DNA nanostructures.}, journal = {Nature Communications}, volume = {14}, year = {2023}, month = {2023 Aug 29}, pages = {5256}, abstract = {

Small unilamellar vesicles (SUVs) are indispensable model membranes, organelle mimics, and drug and vaccine carriers. However, the lack of robust techniques to functionalize or organize preformed SUVs limits their applications. Here we use DNA nanostructures to coat, cluster, and pattern sub-100-nm liposomes, generating distance-controlled vesicle networks, strings and dimers, among other configurations. The DNA coating also enables attachment of proteins to liposomes, and temporal control of membrane fusion driven by SNARE protein complexes. Such a convenient and versatile method of engineering premade vesicles both structurally and functionally is highly relevant to bottom-up biology and targeted delivery.

}, keywords = {Blister, DNA, Engineering, Humans, Liposomes, Nanostructures, Polymers}, issn = {2041-1723}, doi = {10.1038/s41467-023-41013-2}, author = {Zhang, Zhao and Feng, Zhaomeng and Zhao, Xiaowei and Jean, Dominique and Yu, Zhiheng and Chapman, Edwin R} } @article {68957, title = {Hydrophobic interactions dominate the recognition of a KRAS G12V neoantigen.}, journal = {Nature Communications}, volume = {14}, year = {2023}, month = {2023 Aug 21}, pages = {5063}, abstract = {

Specificity remains a major challenge to current therapeutic strategies for cancer. Mutation associated neoantigens (MANAs) are products of genetic alterations, making them highly specific therapeutic targets. MANAs are HLA-presented (pHLA) peptides derived from intracellular mutant proteins that are otherwise inaccessible to antibody-based therapeutics. Here, we describe the cryo-EM structure of an antibody-MANA pHLA complex. Specifically, we determine a TCR mimic (TCRm) antibody bound to its MANA target, the KRAS peptide presented by HLA-A*03:01. Hydrophobic residues appear to account for the specificity of the mutant G12V residue. We also determine the structure of the wild-type G12 peptide bound to HLA-A*03:01, using X-ray crystallography. Based on these structures, we perform screens to validate the key residues required for peptide specificity. These experiments led us to a model for discrimination between the mutant and the wild-type peptides presented on HLA-A*03:01 based exclusively on hydrophobic interactions.

}, keywords = {Antibodies, HLA-A Antigens, Hydrophobic and Hydrophilic Interactions, Proto-Oncogene Proteins p21(ras), Recognition, Psychology}, issn = {2041-1723}, doi = {10.1038/s41467-023-40821-w}, author = {Wright, Katharine M and DiNapoli, Sarah R and Miller, Michelle S and Aitana Azurmendi, P and Zhao, Xiaowei and Yu, Zhiheng and Chakrabarti, Mayukh and Shi, WuXian and Douglass, Jacqueline and Hwang, Michael S and Hsiue, Emily Han-Chung and Mog, Brian J and Pearlman, Alexander H and Paul, Suman and Konig, Maximilian F and Pardoll, Drew M and Bettegowda, Chetan and Papadopoulos, Nickolas and Kinzler, Kenneth W and Vogelstein, Bert and Zhou, Shibin and Gabelli, Sandra B} } @article {68562, title = {In situ cryo-electron tomography reveals the asymmetric architecture of mammalian sperm axonemes.}, journal = {Nature Structural \& Molecular Biology}, volume = {30}, year = {2023}, month = {2023 Mar 01}, pages = {360-9}, abstract = {

The flagella of mammalian sperm display non-planar, asymmetric beating, in contrast to the planar, symmetric beating of flagella from sea urchin sperm and unicellular organisms. The molecular basis of this difference is unclear. Here, we perform in situ cryo-electron tomography of mouse and human sperm, providing the highest-resolution structural information to date. Our subtomogram averages reveal mammalian sperm-specific protein complexes within the microtubules, the radial spokes and nexin-dynein regulatory complexes. The locations and structures of these complexes suggest potential roles in enhancing the mechanical strength of mammalian sperm axonemes and regulating dynein-based axonemal bending. Intriguingly, we find that each of the nine outer microtubule doublets is decorated with a distinct combination of sperm-specific complexes. We propose that this asymmetric distribution of proteins differentially regulates the sliding of each microtubule doublet and may underlie the asymmetric beating of mammalian sperm.

}, issn = {1545-9985}, doi = {10.1038/s41594-022-00861-0}, author = {Chen, Zhen and Greenan, Garrett A and Shiozaki, Momoko and Liu, Yanxin and Skinner, Will M and Zhao, Xiaowei and Zhao, Shumei and Yan, Rui and Yu, Zhiheng and Lishko, Polina V and Agard, David A and Vale, Ronald D} } @article {65658, title = {Microdomains form on the luminal face of neuronal extracellular vesicle membranes.}, journal = {Scientific Reports}, volume = {10}, year = {2020}, month = {2020 Jul 20}, pages = {11953}, abstract = {

Extracellular vesicles (EVs) are important mediators of cell-to-cell communication and have been implicated in several pathologies including those of the central nervous system. They are released by all cell types, including neurons, and are highly heterogenous in size and composition. Yet much remains unknown regarding the biophysical characteristics of different EVs. Here, using cryo-electron microscopy (cryoEM), we analyzed the size distribution and morphology of EVs released from primary cortical neurons. We discovered massive macromolecular clusters on the luminal face of EV membranes. These clusters are predominantly found on medium-sized vesicles, suggesting that they may be specific to microvesicles as opposed to exosomes. We propose that these clusters serve as microdomains for EV signaling and play an important role in EV physiology.

}, issn = {2045-2322}, doi = {10.1038/s41598-020-68436-x}, author = {Matthies, Doreen and Lee, Nathanael Y J and Gatera, Ian and Pasolli, H Amalia and Zhao, Xiaowei and Liu, Hui and Walpita, Deepika and Liu, Zhe and Yu, Zhiheng and Ioannou, Maria S} }