cGAS recruitment to micronuclei is dictated by pre-existing nuclear chromatin status

Kate M. MacDonald, Shirony Nicholson-Puthenveedu, Maha M. Tageldein, Cheryl Arrowsmith, Shane M. Harding

Preprint posted on 13 January 2022

Inflammation upon DNA damage: it takes two to tango!

Selected by Roberto Amadio


Background. DNA damage or problems during DNA replication or cell division can lead to the formation of micronuclei (MN), extra-nuclear compartments where damaged DNA ends up. The envelope of micronuclei is intrinsically unstable, due to defects in the nuclear lamina or nuclear pore complex proteins (Kwon et al. 2020). This MN fragility further promotes DNA damage, tumor progression and DNA release into the cytosol, with consequent activation of an inflammatory cascade. DNA exposed outside canonical compartments such as nuclei is rapidly sensed by the innate receptor cGAS, which in turn alert the cell about the on-going damage by producing inflammatory mediators.

MN envelope break down is currently thought to be the primary event leading to cGAS recruitment and activation inside MN. To date, MN stability is associated with the presence of structural factors such as Lamin A/C (Sepaniac et al. 2021) or the amount of DNA content (Mammel et al., 2021). To date, the only factor able to restrain cGAS activation upon MN break down is the DNAse TREX1, which actively degrades MN DNA (Mohr et al. 2021). But, you know, it takes two to tango…so, are there any other players that influence whether a MN will lead to cGAS recruitment and/or activation? What about the nature of damaging agents or MN composition?


Key findings of this preprint

1) cGAS has a different taste for MN according to the genotoxic agent
Prompted by these compelling questions, the authors of this preprint started asking whether different genotoxic insults generate different MN flavors. They used several stressors, such as ionizing radiation (IR), the base-alkylating agent methyl methanesulfonate (MMS), the RNA polymerase II inhibitor 5,6-dichloro-1-beta-ribo-furanosyl benzimidazole (DRB), and an siRNA-mediated knockdown of serine/arginine-rich splicing factor 1 (SRSF1), a pre-mRNA splicing protein. Treatments that gave the higher proportion of MN positive for the DNA damage marker γH2AX also scored higher for cGAS accumulation, suggesting that some intrinsic MN features might favor cGAS recruitment.


2) MN rupture is not sufficient for cGAS recruitment
The different treatments used did not differ in the probability of MN break up after acute stressor exposure. However, while in control cells, cGAS+ MN occurred in ≈ 60% of ruptured MN and in ≈ 30% of intact MN; treated cells showed varying degree of cGAS accumulation (figure 1). Particularly, MMS treatment showed the highest cGAS score both in intact and ruptured MN, whereas siSRF1 showed the lowest. This observation suggests that MN break up is not sufficient per se to allow cGAS to sense MN DNA, indicating the potential existence of other MN-intrinsic cGAS regulators.

Figure 1 – Quantification of cGAS recruitment to intact or ruptured MN, according to the upstream stressor.


3) MN with active chromatin are void of cGAS
One such regulator appears to be active chromatin. Treatments inducing acute transcription stress (i.e. siSRF1), generate a higher degree of active chromatin-containing MN, which inversely correlates with cGAS staining (figure 2). As a possible explanation the authors suggested that components of the transcriptional machinery might inhibit cGAS recruitment, but this interesting interplay will warrant further investigation.

Figure 2 – Inverse correlation between cGAS presence and active chromatin in MN.


4) cGAS binds to H3K79me2
Apart from chromatin conformation and the presence of physical impediment, other factors potentially involved in cGAS-MN tango can be found in the plethora of post-translational modifications occurring at the chromatin level. The authors used a library of chemical inhibitors, specifically designed to target chromatin readers, writers, and erasers. The top hit of the screening was the methyltransferase DOT1L, the only one known to be responsible for di-methylation of lysine 79 on histone 3 (H3K79me2). Inhibiting DOT1L significatively blunted cGAS recruitment to MN. Adding another line of evidence in this direction, cGAS was also found to immunoprecipitated with H3K79me2.


5) Epigenetic targeting of MN chromatin can be used to modulate MN-driven inflammation
Given the impact of cGAS-directed MN-DNA recognition of the inflammatory phenotype of the cell, the author validated the possibility of modulating production of interferon responsive genes (ISGs) by leveraging the notions gained throughout the work. Indeed, DOT1L inhibition ameliorated the inflammatory phenotype in irradiated cells. cGAS knock-out or treatment with CDK1 inhibitor (to block mitosis and therefore MN production) impaired ISGs production, confirming the importance of cGAS-MN tango to produce an inflammatory phenotype. DOT1L inhibition underscored the importance of chromatin status in dictating cGAS activation and add another piece of complexity in the exciting field of cGAS biology.


Why I chose this preprint

The question addressed by the authors is not trivial and the experiments described in the preprint were clearly and rigorously planned. I like the attempt to dissect the molecular players that regulate the fate of MN and whether MN will become highly immunogenic for cGAS or not. I appreciate how the authors were able to perform clever experiments and discuss them using clear language, even though the topic is not actually so easy to understand for people outside the “DNA damage field” of research.


Questions to the authors

  • Is there a way for a cell with micronuclei to clear them and recover from the insult or once MN are formed, they persist and eventually will irreparably damage the cell?
  • Is cGAS the only DNA sensor known to be activated inside MN?
  • H3K79me2 is involved in the DNA damage response. Does DOT1Li blunt only cGAS localization inside MN or also general nuclear cGAS localization?



  • Kwon, M., Leibowitz, M.L. & Lee, JH. “Small but mighty: the causes and consequences of micronucleus rupture.” Exp Mol Med 52, 1777–1786 (2020).
  • Sepaniac, L.A., Martin, W., Dionne, L.A., Stearns, T.M., Reinholdt, L.G. and Stumpff, J. (2021) “Micronuclei in Kif18a mutant mice form stable micronuclear envelopes and do not promote tumorigenesis.” Journal of Cell Biology, 220(11) 34.
  • Mammel, A.E., Huang, H.Z., Gunn, A.L., Choo, E. and Hatch, E.M. (2022) “Chromosome length and gene density contribute to micronuclear membrane stability.” Life Science Alliance, 5(2), p. e202101210. doi:10.26508/lsa.20210121026.
  • Mohr, L., Toufektchan, E., von Morgen, P., Chu, K., Kapoor, A. and Maciejowski, J. (2021) “ER-directed TREX1 limits cGAS activation at micronuclei.” Molecular Cell, 0(0), pp. 1–15. doi:10.1016/j.molcel.2020.12.03728.


Tags: cgas, ddr, dna damage, inflammation, micronuclei

Posted on: 1 February 2022


Read preprint (No Ratings Yet)

Have your say

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Sign up to customise the site to your preferences and to receive alerts

Register here

preLists in the cell biology category:


The advances in fibroblast biology preList explores the recent discoveries and preprints of the fibroblast world. Get ready to immerse yourself with this list created for fibroblasts aficionados and lovers, and beyond. Here, my goal is to include preprints of fibroblast biology, heterogeneity, fate, extracellular matrix, behavior, topography, single-cell atlases, spatial transcriptomics, and their matrix!


List by Osvaldo Contreras

EMBL Synthetic Morphogenesis: From Gene Circuits to Tissue Architecture (2021)

A list of preprints mentioned at the #EESmorphoG virtual meeting in 2021.


List by Alex Eve

FENS 2020

A collection of preprints presented during the virtual meeting of the Federation of European Neuroscience Societies (FENS) in 2020


List by Ana Dorrego-Rivas

Planar Cell Polarity – PCP

This preList contains preprints about the latest findings on Planar Cell Polarity (PCP) in various model organisms at the molecular, cellular and tissue levels.


List by Ana Dorrego-Rivas

BioMalPar XVI: Biology and Pathology of the Malaria Parasite

[under construction] Preprints presented at the (fully virtual) EMBL BioMalPar XVI, 17-18 May 2020 #emblmalaria


List by Dey Lab, Samantha Seah


Cell Polarity

Recent research from the field of cell polarity is summarized in this list of preprints. It comprises of studies focusing on various forms of cell polarity ranging from epithelial polarity, planar cell polarity to front-to-rear polarity.


List by Yamini Ravichandran

TAGC 2020

Preprints recently presented at the virtual Allied Genetics Conference, April 22-26, 2020. #TAGC20


List by Maiko Kitaoka et al.

3D Gastruloids

A curated list of preprints related to Gastruloids (in vitro models of early development obtained by 3D aggregation of embryonic cells). Updated until July 2021.


List by Paul Gerald L. Sanchez and Stefano Vianello

ECFG15 – Fungal biology

Preprints presented at 15th European Conference on Fungal Genetics 17-20 February 2020 Rome


List by Hiral Shah

ASCB EMBO Annual Meeting 2019

A collection of preprints presented at the 2019 ASCB EMBO Meeting in Washington, DC (December 7-11)


List by Madhuja Samaddar et al.

EMBL Seeing is Believing – Imaging the Molecular Processes of Life

Preprints discussed at the 2019 edition of Seeing is Believing, at EMBL Heidelberg from the 9th-12th October 2019


List by Dey Lab


Preprints on autophagy and lysosomal degradation and its role in neurodegeneration and disease. Includes molecular mechanisms, upstream signalling and regulation as well as studies on pharmaceutical interventions to upregulate the process.


List by Sandra Malmgren Hill

Lung Disease and Regeneration

This preprint list compiles highlights from the field of lung biology.


List by Rob Hynds

Cellular metabolism

A curated list of preprints related to cellular metabolism at Biorxiv by Pablo Ranea Robles from the Prelights community. Special interest on lipid metabolism, peroxisomes and mitochondria.


List by Pablo Ranea Robles

BSCB/BSDB Annual Meeting 2019

Preprints presented at the BSCB/BSDB Annual Meeting 2019


List by Dey Lab


This list of preprints is focused on work expanding our knowledge on mitochondria in any organism, tissue or cell type, from the normal biology to the pathology.


List by Sandra Franco Iborra

Biophysical Society Annual Meeting 2019

Few of the preprints that were discussed in the recent BPS annual meeting at Baltimore, USA


List by Joseph Jose Thottacherry

ASCB/EMBO Annual Meeting 2018

This list relates to preprints that were discussed at the recent ASCB conference.


List by Dey Lab, Amanda Haage