Browsing by Author "Nir, Guy"

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    Chromatin alternates between A and B compartments at kilobase scale for subgenic organization
    (Springer Nature, 2023) Harris, Hannah L.; Gu, Huiya; Olshansky, Moshe; Wang, Ailun; Farabella, Irene; Eliaz, Yossi; Kalluchi, Achyuth; Krishna, Akshay; Jacobs, Mozes; Cauer, Gesine; Pham, Melanie; Rao, Suhas S. P.; Dudchenko, Olga; Omer, Arina; Mohajeri, Kiana; Kim, Sungjae; Nichols, Michael H.; Davis, Eric S.; Gkountaroulis, Dimos; Udupa, Devika; Aiden, Aviva Presser; Corces, Victor G.; Phanstiel, Douglas H.; Noble, William Stafford; Nir, Guy; Di Pierro, Michele; Seo, Jeong-Sun; Talkowski, Michael E.; Aiden, Erez Lieberman; Rowley, M. Jordan; Center for Theoretical Biological Physics
    Nuclear compartments are prominent features of 3D chromatin organization, but sequencing depth limitations have impeded investigation at ultra fine-scale. CTCF loops are generally studied at a finer scale, but the impact of looping on proximal interactions remains enigmatic. Here, we critically examine nuclear compartments and CTCF loop-proximal interactions using a combination of in situ Hi-C at unparalleled depth, algorithm development, and biophysical modeling. Producing a large Hi-C map with 33 billion contacts in conjunction with an algorithm for performing principal component analysis on sparse, super massive matrices (POSSUMM), we resolve compartments to 500 bp. Our results demonstrate that essentially all active promoters and distal enhancers localize in the A compartment, even when flanking sequences do not. Furthermore, we find that the TSS and TTS of paused genes are often segregated into separate compartments. We then identify diffuse interactions that radiate from CTCF loop anchors, which correlate with strong enhancer-promoter interactions and proximal transcription. We also find that these diffuse interactions depend on CTCF’s RNA binding domains. In this work, we demonstrate features of fine-scale chromatin organization consistent with a revised model in which compartments are more precise than commonly thought while CTCF loops are more protracted.
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    Walking along chromosomes with super-resolution imaging, contact maps, and integrative modeling
    (Public Library of Science, 2018) Nir, Guy; Farabella, Irene; Estrada, Cynthia Pérez; Ebeling, Carl G.; Beliveau, Brian J.; Sasaki, Hiroshi M.; Lee, S. Dean; Nguyen, Son C.; McCole, Ruth B.; Chattoraj, Shyamtanu; Erceg, Jelena; Abed, Jumana AlHaj; Martins, Nuno M.C.; Nguyen, Huy Q.; Hannan, Mohammed A.; Russell, Sheikh; Durand, Neva C.; Rao, Suhas S.P.; Kishi, Jocelyn Y.; Soler-Vila, Paula; Pierro, Michele Di; Onuchic, José N.; Callahan, Steven P.; Schreiner, John M.; Stuckey, Jeff A.; Yin, Peng; Aiden, Erez Lieberman; Marti-Renom, Marc A.; Wu, C.-ting
    Chromosome organization is crucial for genome function. Here, we present a method for visualizing chromosomal DNA at super-resolution and then integrating Hi-C data to produce three-dimensional models of chromosome organization. Using the super-resolution microscopy methods of OligoSTORM and OligoDNA-PAINT, we trace 8 megabases of human chromosome 19, visualizing structures ranging in size from a few kilobases to over a megabase. Focusing on chromosomal regions that contribute to compartments, we discover distinct structures that, in spite of considerable variability, can predict whether such regions correspond to active (A-type) or inactive (B-type) compartments. Imaging through the depths of entire nuclei, we capture pairs of homologous regions in diploid cells, obtaining evidence that maternal and paternal homologous regions can be differentially organized. Finally, using restraint-based modeling to integrate imaging and Hi-C data, we implement a method-integrative modeling of genomic regions (IMGR)-to increase the genomic resolution of our traces to 10 kb.