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The innate immune sensor IFI16 recognizes foreign DNA in the nucleus by scanning along the duplex.

Stratmann SA, Morrone SR, van Oijen AM, Sohn J - Elife (2015)

Bottom Line: However, the molecular mechanisms underlying distinction between foreign DNA and host genomic material inside the nucleus are not understood.We also demonstrate that nucleosomes represent barriers that prevent IFI16 from targeting host DNA by directly interfering with these one-dimensional movements.This unique scanning-assisted assembly mechanism allows IFI16 to distinguish friend from foe and assemble into oligomers efficiently and selectively on foreign DNA.

View Article: PubMed Central - PubMed

Affiliation: University of Groningen, Groningen, Netherlands.

ABSTRACT
The ability to recognize foreign double-stranded (ds)DNA of pathogenic origin in the intracellular environment is an essential defense mechanism of the human innate immune system. However, the molecular mechanisms underlying distinction between foreign DNA and host genomic material inside the nucleus are not understood. By combining biochemical assays and single-molecule techniques, we show that the nuclear innate immune sensor IFI16 one-dimensionally tracks long stretches of exposed foreign dsDNA to assemble into supramolecular signaling platforms. We also demonstrate that nucleosomes represent barriers that prevent IFI16 from targeting host DNA by directly interfering with these one-dimensional movements. This unique scanning-assisted assembly mechanism allows IFI16 to distinguish friend from foe and assemble into oligomers efficiently and selectively on foreign DNA.

No MeSH data available.


Related in: MedlinePlus

Single-molecule co-localization probability of anti-H4- Atto488 with IFI16-Cy5 on nucleosomal biotin-λdsDNA and on biotin-601-nucleosomes (N = 419 and 472, respectively).601-nucleosomes do not provide sufficient exposed dsDNA for IFI16 binding, whereas on λdsDNA IFI16 molecules travel until encountering nucleosome obstacles.DOI:http://dx.doi.org/10.7554/eLife.11721.016
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fig4s2: Single-molecule co-localization probability of anti-H4- Atto488 with IFI16-Cy5 on nucleosomal biotin-λdsDNA and on biotin-601-nucleosomes (N = 419 and 472, respectively).601-nucleosomes do not provide sufficient exposed dsDNA for IFI16 binding, whereas on λdsDNA IFI16 molecules travel until encountering nucleosome obstacles.DOI:http://dx.doi.org/10.7554/eLife.11721.016

Mentions: To test whether the inhibitory effect of chromatin directly arises by interfering with the 1D diffusion of IFI16, we visualized the movement of individual IFI16 molecules on DNA with nucleosomes. We introduced randomly localized nucleosomes in λdsDNA using recombinant human histone octamers and tagged nucleosome positions with fluorescent antibodies against the N-terminal tail of histone H4 (Figure 4—figure supplement 1). The application of hydrodynamic flow resulted in the single IFI16 molecules being pushed to one direction and clustering at nucleosomal sites on λdsDNA, unable to overcome the octamers by diffusion (Figure 4A, Figure 4—figure supplement 2, and Video 3). Without the antibody, the motion of IFI16 was still confined, whereas for bare λdsDNA, IFI16 moved with a high processivity along the entire strand (Figures 4B,C, and Figure 4—figure supplement 3). These observations are consistent with the bulk experiments (Figure 3), and confirm that nucleosomes directly restrict the 1D diffusion of IFI16 and consequently limit the assembly of IFI16 signaling platforms on dsDNA.10.7554/eLife.11721.014Figure 4.Nucleosomes inhibit 1D-diffusion.


The innate immune sensor IFI16 recognizes foreign DNA in the nucleus by scanning along the duplex.

Stratmann SA, Morrone SR, van Oijen AM, Sohn J - Elife (2015)

Single-molecule co-localization probability of anti-H4- Atto488 with IFI16-Cy5 on nucleosomal biotin-λdsDNA and on biotin-601-nucleosomes (N = 419 and 472, respectively).601-nucleosomes do not provide sufficient exposed dsDNA for IFI16 binding, whereas on λdsDNA IFI16 molecules travel until encountering nucleosome obstacles.DOI:http://dx.doi.org/10.7554/eLife.11721.016
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4829420&req=5

fig4s2: Single-molecule co-localization probability of anti-H4- Atto488 with IFI16-Cy5 on nucleosomal biotin-λdsDNA and on biotin-601-nucleosomes (N = 419 and 472, respectively).601-nucleosomes do not provide sufficient exposed dsDNA for IFI16 binding, whereas on λdsDNA IFI16 molecules travel until encountering nucleosome obstacles.DOI:http://dx.doi.org/10.7554/eLife.11721.016
Mentions: To test whether the inhibitory effect of chromatin directly arises by interfering with the 1D diffusion of IFI16, we visualized the movement of individual IFI16 molecules on DNA with nucleosomes. We introduced randomly localized nucleosomes in λdsDNA using recombinant human histone octamers and tagged nucleosome positions with fluorescent antibodies against the N-terminal tail of histone H4 (Figure 4—figure supplement 1). The application of hydrodynamic flow resulted in the single IFI16 molecules being pushed to one direction and clustering at nucleosomal sites on λdsDNA, unable to overcome the octamers by diffusion (Figure 4A, Figure 4—figure supplement 2, and Video 3). Without the antibody, the motion of IFI16 was still confined, whereas for bare λdsDNA, IFI16 moved with a high processivity along the entire strand (Figures 4B,C, and Figure 4—figure supplement 3). These observations are consistent with the bulk experiments (Figure 3), and confirm that nucleosomes directly restrict the 1D diffusion of IFI16 and consequently limit the assembly of IFI16 signaling platforms on dsDNA.10.7554/eLife.11721.014Figure 4.Nucleosomes inhibit 1D-diffusion.

Bottom Line: However, the molecular mechanisms underlying distinction between foreign DNA and host genomic material inside the nucleus are not understood.We also demonstrate that nucleosomes represent barriers that prevent IFI16 from targeting host DNA by directly interfering with these one-dimensional movements.This unique scanning-assisted assembly mechanism allows IFI16 to distinguish friend from foe and assemble into oligomers efficiently and selectively on foreign DNA.

View Article: PubMed Central - PubMed

Affiliation: University of Groningen, Groningen, Netherlands.

ABSTRACT
The ability to recognize foreign double-stranded (ds)DNA of pathogenic origin in the intracellular environment is an essential defense mechanism of the human innate immune system. However, the molecular mechanisms underlying distinction between foreign DNA and host genomic material inside the nucleus are not understood. By combining biochemical assays and single-molecule techniques, we show that the nuclear innate immune sensor IFI16 one-dimensionally tracks long stretches of exposed foreign dsDNA to assemble into supramolecular signaling platforms. We also demonstrate that nucleosomes represent barriers that prevent IFI16 from targeting host DNA by directly interfering with these one-dimensional movements. This unique scanning-assisted assembly mechanism allows IFI16 to distinguish friend from foe and assemble into oligomers efficiently and selectively on foreign DNA.

No MeSH data available.


Related in: MedlinePlus