Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session F10: Liquid Phases, Spatial Genome Organization, and TranscriptionInvited Live
|
Hide Abstracts |
Sponsoring Units: DBIO Chair: William Bialek, Princeton University |
Tuesday, March 16, 2021 11:30AM - 12:06PM Live |
F10.00001: A Model For Chromatin Organization Through Liquid-Liquid Phase Separation Invited Speaker: Michael Rosen Biomolecular condensates are two- and three-dimensional compartments in eukaryotic cells that concentrate specific collections of proteins and nucleic acids without an encapsulating membrane. Many condensates behave as dynamic liquids, and are believed to form through liquid-liquid phase separation (LLPS) driven by interactions between multivalent macromolecules. Efforts in my lab have recently expanded in a new direction, to understand whether and how LLPS might regulate the organization of chromatin in the eukaryotic cell nucleus. In my talk I will discuss our finding that polynucleosome arrays, which mimic the multivalent chromatin polymer, have an intrinsic capacity to undergo LLPS. Moreover, many factors known to control chromatin organization in cells have parallel effects on phase separated chromatin droplets in vitro, including histone H1, internucleosome spacing and histone tail acetylation. Our data suggest a new framework, based on intrinsic phase separation of the chromatin polymer, to understand the organization and regulation of eukaryotic genomes. |
Tuesday, March 16, 2021 12:06PM - 12:42PM Live |
F10.00002: The dynamics of gene expression, from the nucleus to mitochondria Invited Speaker: L. Stirling Churchman In this talk I will discuss our ongoing efforts to investigate gene regulatory processes occurring throughout the cell, from the nucleus to the mitochondria. We established native elongating transcript sequencing (NET-seq) and nanopore analysis of co-transcriptional processing (nano-COP) that probe transcription elongation and co-transcriptional processing. These approaches monitor where, when and how splicing occurs across long human nascent transcripts that contain multiple introns. Intriguingly, we found that proximal introns are more often spliced together than introns spaced apart, indicating that splicing of proximal introns is coordinated. |
Tuesday, March 16, 2021 12:42PM - 1:18PM Live |
F10.00003: No membrane, no problem: Condensing bacterial organelles Invited Speaker: Stephanie C Weber Living cells are divided into functional compartments called organelles. In eukaryotes, lipid membranes separate organelles from the cytoplasm such that each compartment maintains a distinct biochemical composition that is tailored to its function. In contrast, prokaryotes typically lack internal membranes and instead must use other mechanisms to spatially organize the cell. Using fluorescence imaging and single-molecule tracking, we show that E. coli RNA polymerase (RNAP) organizes into clusters through liquid-liquid phase separation (LLPS). RNAP clusters, or "condensates", increase cell survival during stress, and appear to regulate ribosome biogenesis in response to nutrient availability. Our results demonstrate that bacteria, like eukaryotic cells, use LLPS to generate membraneless organelles that spatially organize biochemical processes to optimize cell fitness in various environments. |
Tuesday, March 16, 2021 1:18PM - 1:54PM Live |
F10.00004: Action at a distance in transcriptional regulation Invited Speaker: Thomas Gregor The three-dimensional organization of chromatin in the cell nucleus has profound consequences on the functional state of the system in terms of gene activity. However, the exact cause and consequence of this organization with respect to transcriptional activity remains elusive. For example, there is evidence that protein binding to specific sites along DNA called enhancers can activate the reading out of genetic information of genes separated by tens or hundreds of thousands of base pairs along the DNA. How does this separation translate into actual distances in physical space at the moment of gene activation? An approach based on high-resolution multi-color imaging is presented to discriminate the specificity of various DNA elements in establishing and maintaining discrete chromosomal configurations at the single cell level. Specifically, targeting a locus with multiple enhancers driving expression in distinct spatial domains in a developing embryo, we simultaneously measure the position of regulatory elements inside and outside their domains of control, and establish specific links between spatial enhancer-promoter configurations and expression domains. Results are presented that suggest a tight relationship between gene activity and specific spatial chromatin arrangements. In particular transcription causes a local decompaction in conjunction with sustained enhancer-specific proximity. The magnitude of this proximity is too large, however, to imply that there is direct contact between the activating enhancer and the active promoter. How then can information about gene activity travel from the enhancer to the promoter across several hundred nanometer through a liquid physical space? |
Tuesday, March 16, 2021 1:54PM - 2:30PM Live |
F10.00005: Super-resolution imaging of transcription in living cells Invited Speaker: Ibrahim Cisse We will discuss the latest efforts in our laboratory to develop highly sensitive methods of microscopy, to go directly inside living cells and uncover the behavior of single biomolecules as they effect their function in transcription. Transcription is the first step in gene expression regulation, during which genetic information on DNA is decoded into RNA transcripts. Methodologically, the so-called live cell single molecule and super-resolution techniques – that break the optical diffraction limit– are revealing with unprecedented spatial and temporal resolutions, novel emergent phenomena inside the living cells. We will discuss our recent discoveries on highly dynamic biomolecular clustering, and phase transitions in vivo. These discoveries are challenging the ‘textbook view’ on how our genome (DNA) is decoded in living cells. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700