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Main Authors: Mitra, Debarshi, Sommer, Jens-Uwe
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2604.02838
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author Mitra, Debarshi
Sommer, Jens-Uwe
author_facet Mitra, Debarshi
Sommer, Jens-Uwe
contents Along the bacterial chromosome, regions called rrn operons contain genes that are transcribed into ribosomal RNA. These operons are among the most transcriptionally active sites in the genome. It has been observed in E. coli that RNA polymerase (RNAP), while binding to these genetic loci along the chromosome during transcription, forms dense clusters, leading to spatial colocalization of the operons within the cell. Recent experimental evidence suggests that liquid-liquid phase separation contributes to the formation of RNAP clusters, with the antitermination factor NusA playing a key role. We present a simulation model to investigate the mechanisms underlying the formation of these biomolecular condensates. We propose that mutual attraction between NusA proteins, which exhibit a miscibility gap at higher concentrations, drives condensate formation via a polymer-assisted condensation pathway, and we demonstrate how these condensates promote the colocalization of rrn operons. Our results reconcile seemingly disparate experimental observations of chromosomal organization reported in fluorescence-based imaging and Hi-C experiments.
format Preprint
id arxiv_https___arxiv_org_abs_2604_02838
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Mechanistic insights into the spatial organization of RNA polymerase proteins and the chromosome in E. coli cells
Mitra, Debarshi
Sommer, Jens-Uwe
Soft Condensed Matter
Along the bacterial chromosome, regions called rrn operons contain genes that are transcribed into ribosomal RNA. These operons are among the most transcriptionally active sites in the genome. It has been observed in E. coli that RNA polymerase (RNAP), while binding to these genetic loci along the chromosome during transcription, forms dense clusters, leading to spatial colocalization of the operons within the cell. Recent experimental evidence suggests that liquid-liquid phase separation contributes to the formation of RNAP clusters, with the antitermination factor NusA playing a key role. We present a simulation model to investigate the mechanisms underlying the formation of these biomolecular condensates. We propose that mutual attraction between NusA proteins, which exhibit a miscibility gap at higher concentrations, drives condensate formation via a polymer-assisted condensation pathway, and we demonstrate how these condensates promote the colocalization of rrn operons. Our results reconcile seemingly disparate experimental observations of chromosomal organization reported in fluorescence-based imaging and Hi-C experiments.
title Mechanistic insights into the spatial organization of RNA polymerase proteins and the chromosome in E. coli cells
topic Soft Condensed Matter
url https://arxiv.org/abs/2604.02838