The N-Terminal Domain of cGAS Determines Preferential Association with Centromeric DNA and Innate Immune Activation in the Nucleus

Abstract

Summary Cytosolic DNA activates cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS), an innate immune sensor pivotal in anti-microbial defense, senescence, auto-immunity, and cancer. cGAS is considered to be a sequence-independent DNA sensor with limited access to nuclear DNA because of compartmentalization. However, the nuclear envelope is a dynamic barrier, and cGAS is present in the nucleus. Here, we identify determinants of nuclear cGAS localization and activation. We show that nuclear-localized cGAS synthesizes cGAMP and induces innate immune activation of dendritic cells, although cGAMP levels are 200-fold lower than following transfection with exogenous DNA. Using cGAS ChIP-seq and a GFP-cGAS knockin mouse, we find nuclear cGAS enrichment on centromeric satellite DNA, confirmed by imaging, and to a lesser extent on LINE elements. The non-enzymatic N-terminal domain of cGAS determines nucleo-cytoplasmic localization, enrichment on centromeres, and activation of nuclear-localized cGAS. These results reveal a preferential functional association of nuclear cGAS with centromeres.

Characterization of cGAS homologs in innate and adaptive mucosal immunities in zebrafish gives evolutionary insights into cGAS‐STING pathway

“…The cGAS‐STING signaling pathway plays diverse roles in innate immunological activities 54‐56 . However, the functional performance of the cGAS‐STING pathway in adaptive mucosal immunity remains largely unknown.…”

Chromatin‐bound cGAS is an inhibitor of DNA repair and hence accelerates genome destabilization and cell death

“…cGAS is generally considered as a cytosolic protein but transiently accumulates in the nucleus following mitotic nuclear membrane dissolution (Yang et al, 2017;Gentili et al, 2019;Zierhut et al, 2019). Moreover, cGAS has also been reported to actively translocate from the cytosol into the nucleus upon DNA damage (Liu et al, 2018) but also localizes to the plasma membrane in some cell types (Barnett et al, 2019).…”

ER-directed TREX1 limits cGAS recognition of micronuclei

“…Likewise, we could not detect increased MN-independent, cytosolic dsDNA levels after TREX1 deletion or Mps1 inhibition ( Figure S5E-H). cGAS exists in nuclear and cytosolic fractions, associating with chromatin following mitotic NE breakdown and accumulating in the cytosol during the subsequent cell cycle (Gentili et al, 2019;Volkman et al, 2019;Yang et al, 2017). We reasoned that unexpected alterations in cGAS subcellular distribution may increase 2 3 -cGAMP in the TREX1 KO cells.…”