The anatomy of transcriptionally active chromatin loops in Drosophila primary spermatocytes using super-resolution microscopy.


Type
Article
Change log
Authors
Ball, Madeleine L 
Koestler, Stefan A 
Rehman, Sohaib Abdul 
O'Holleran, Kevin 
Abstract

While the biochemistry of gene transcription has been well studied, our understanding of how this process is organised in 3D within the intact nucleus is less well understood. Here we investigate the structure of actively transcribed chromatin and the architecture of its interaction with active RNA polymerase. For this analysis, we have used super-resolution microscopy to image the Drosophila melanogaster Y loops which represent huge, several megabases long, single transcription units. The Y loops provide a particularly amenable model system for transcriptionally active chromatin. We find that, although these transcribed loops are decondensed they are not organised as extended 10nm fibres, but rather they largely consist of chains of nucleosome clusters. The average width of each cluster is around 50nm. We find that foci of active RNA polymerase are generally located off the main fibre axis on the periphery of the nucleosome clusters. Foci of RNA polymerase and nascent transcripts are distributed around the Y loops rather than being clustered in individual transcription factories. However, as the RNA polymerase foci are considerably less prevalent than the nucleosome clusters, the organisation of this active chromatin into chains of nucleosome clusters is unlikely to be determined by the activity of the polymerases transcribing the Y loops. These results provide a foundation for understanding the topological relationship between chromatin and the process of gene transcription.

Description

Funder: Higher Education Commision, Pakistan


Funder: Cambridge Trust


Funder: Isaac Newton Trust

Keywords
Male, Animals, Drosophila, Microscopy, Drosophila melanogaster, Nucleosomes, Spermatocytes, Transcription, Genetic, Chromatin, DNA-Directed RNA Polymerases
Journal Title
PLoS Genet
Conference Name
Journal ISSN
1553-7404
1553-7404
Volume Title
19
Publisher
Public Library of Science (PLoS)
Sponsorship
Isaac Newton Trust (21.39(f))
Biotechnology and Biological Sciences Research Council (BB/S00758X/1)
BBSRC (2113622)
Engineering and Physical Sciences Research Council (EP/R025398/1)