et al.

Fig. 6. cGAS binds to DNA in the cytoplasm. (A) Nuclear and cytoplasmic fractions were prepared from
THP-1 cells and analyzed by immunoblotting with the indicated antibodies. (B) THP-1 cells were
homogenized in hypotonic buffer and subjected to differential centrifugation. Pellets at different speeds
of centrifugation (e.g., P100: pellets after 100,000g) and S100 were immunoblotted with the indicated
antibodies. (C) L929 cells stably expressing Flag-cGAS (green) were transfected with Cy3-ISD (red). At
different time points after transfection, cells were fixed, stained with antibody to Flag or with 4´,6diamidino-2-phenylindole
(DAPI), and imaged by confocal fluorescence microscopy. The insets in the
merged images are magnifications of the small boxed areas. These images are representative of at least
10 cells at each time point (representing >50% of the cells under examination).
into the host cytoplasm—such as DNA viruses,
bacteria, parasites (e.g., malaria), and retroviruses
(e.g., HIV)—could potentially trigger the cGAS-
STING pathway (14, 15). The enzymatic synthesis
of cGAMP by cGAS provides a mechanism
of signal amplification for a robust and sensitive
immune response. However, the detection of self
DNA in the host cytoplasm by cGAS could also
lead to autoimmune diseases, such as systemic
lupus erythematosus, Sjögren’s syndrome, and
Aicardi-Goutières syndrome (16–18).
Several other DNA sensors, such as DAI,
IFI16, and DDX41, have been reported to in-
Universal Computation by
Multiparticle Quantum Walk
Andrew M. Childs, 1,2 David Gosset, 1,2 * Zak Webb 2,3
duce type I interferons (19–21). Overexpression
of DAI, IFI16, or DDX41 did not lead to
the production of cGAMP. We also found that
knockdown of DDX41 and p204 (a mouse homolog
of IFI16) by siRNA did not inhibit the
generation of cGAMP activity in HT-DNA–
transfected L929 cells (fig. S7). Nonetheless, it
is possible that distinct DNA sensors exist in different
cell types. Unlike other putative DNA
sensors and most pattern recognition receptors
(e.g., TLRs), cGAS is a cyclase that is likely more
amenable to inhibition by small-molecule compounds.
These inhibitors may be developed into
A quantum walk is a time-homogeneous quantum-mechanical process on a graph defined by analogy to
classical random walk. The quantum walker is a particle that moves from a given vertex to adjacent
vertices in quantum superposition. We consider a generalization to interacting systems with more than
onewalker,suchastheBose-Hubbardmodelandsystems of fermions or distinguishable particles with
nearest-neighbor interactions, and show that multiparticle quantum walk is capable of universal quantum
computation. Our construction could, in principle, be used as an architecture for building a scalable
quantum computer with no need for time-dependent control.
Quantum walk is a versatile and intuitive
framework for developing quantum algorithms.
Applications of continuous- (1)
and discrete-time (2, 3) models of quantum walk
include an example of exponential speed-up over
classical computation (4) and optimal algo-
therapeutic agents for the treatment of human
autoimmune diseases.
References and Notes
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32, 574 (2011).
4. J. Wu et al., Science 339, 826 (2013).
5. J. Cox, M. Mann, Nat. Biotechnol. 26, 1367 (2008).
6. K. Kuchta, L. Knizewski, L. S. Wyrwicz, L. Rychlewski,
K. Ginalski, Nucleic Acids Res. 37, 7701 (2009).
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3615 (1995).
8. J. Pei, B. H. Kim, N. V. Grishin, Nucleic Acids Res. 36,
2295 (2008).
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10. Y. H. Chiu, J. B. Macmillan, Z. J. Chen, Cell 138, 576 (2009).
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(2009).
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Cell 149, 358 (2012).
13. Z. H. Chen, P. Schaap, Nature 488, 680 (2012).
14. S. Sharma et al., Immunity 35, 194 (2011).
15. N. Yan, Z. J. Chen, Nat. Immunol. 13, 214 (2012).
16. V. Pascual, L. Farkas, J. Banchereau, Curr. Opin.
Immunol. 18, 676 (2006).
17. Y. Yao, Z. Liu, B. Jallal, N. Shen, L. Ronnblom, Autoimmun.
Rev. 10.1016/j.autrev.2012.10.006 (2012).
18. R. E. Rigby, A. Leitch, A. P. Jackson, Bioessays 30, 833 (2008).
19. A. Takaoka et al., Nature 448, 501 (2007).
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21. Z. Zhang et al., Nat. Immunol. 12, 959 (2011).
Acknowledgments: WethankW.Liforhelpfuldiscussion
on bioinformatics analyses. The GenBank accession numbers
for human and mouse cGAS sequences are KC294566 and
KC294567, respectively. Supported by NIH grant AI-093967.
Z.J.C. is an investigator of Howard Hughes Medical Institute.
Supplementary Materials
www.sciencemag.org/cgi/content/full/science.1232458/DC1
Materials and Methods
Figs. S1 to S7
Table S1
References (22, 23)
7 November 2012; accepted 12 December 2012
Published online 20 December 2012;
10.1126/science.1232458
REPORTS
rithms for element distinctness (5) and formula
evaluation (6).
Quantum walk is also a powerful computational
model capable of performing any quantum
computation (7). However, the graph used to perform
a computation on n qubits is exponentially
large as a function of n. Such a quantum walk
cannot be efficiently implemented using an architecture
where each vertex of the graph occupies
a different spatial location. Nevertheless, many
nonscalable implementations of quantum walk
have been carried out (8–10) despite substantial
1
Department of Combinatorics and Optimization, University of
Waterloo, Waterloo, Ontario N2L 3G1, Canada. 2 Institute for
Quantum Computing, University of Waterloo, Waterloo, Ontario
N2L 3G1, Canada. 3 Department of Physics and Astronomy,
University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
*To whom correspondence should be addressed. E-mail:
dngosset@gmail.com
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