Targeting the cGAS-STING Pathway Using a Homogenous, HTS Compatible Transcreener cGAS Assay

Transcreener cGAMP Assay Kit - TR-FRET Readout

The Transcreener® cGAMP Assay with TR-FRET readout uses displacement of a tracer by cGAMP to measure enzymatic activity. This disrupts FRET from the antibody-bound Terbium chelate leading to a decrease in the TR-FRET signal. In addition to the time-resolved signal, the assay uses a far-red tracer to minimize interference from fluorescent compounds and light scattering.

The assay produces excellent data quality (Z' ≥ 0.7) at cGAMP ranges between 0.5 μM and 100 μM. Both reagents & signal are stable at room temperature for over 24 hours, providing outstanding flexibility for automated high-volume screening programs. The universal detection method allows screening of virtually any cGAMP-producing enzyme in a high throughput format. 

Used in over millions of wells by pharma since 2006, Transcreener is an extensively validated enzyme detection method backed by the best technical support in the industry. 

This assay is designed to be used with purified enzyme preparations. Transcreener assays are not validated with cell lysates, blood, serum, or other biological samples.

Direct Detection of cGAMP to Measure cGAS Enzymatic Activity

Time-Resolved Förster Resonance Energy Transfer (TR-FRET)

cGAMP Assay Kit Schematic - FRET Readout


  • Measure enzymatic activity of cGAS
  • Screen compound libraries for cGAS inhibitors
  • Quantify inhibitor potency
  • Determine inhibitor-cGAS residence time


  • Direct detection of unlabeled cGAMP
  • Easy to use, homogenous, one step format
  • Robust assay Z' > 0.7 under initial velocity conditions
  • Far-red fluorescent readouts minimize compound interference 
  • A safe, non-radioactive method

Example cGAMP Titration

cGAMP Assay Standard Curve TR-FRET

Easy-to-Use, Mix-&-Read, HTS-Ready

Run your enzyme reaction, add Transcreener reagents, and read your plates. The cGAS assay kit is compatible with 96, 384, and 1536-well formats. 


Excellent Z' Down to nM cGAMP Levels

Important Messenger in the STING Pathway

DNA in the cytosol of eukaryotic cells indicates infection or cellular damage, and it elicits a robust immune response, driven by type I interferon (IFN) induction. cGAS is an exquisitely sensitive sensor for double-stranded DNA in the cytoplasm. Binding of DNA activates the enzyme to produce a unique cyclic dinucleotide second messenger, cGAMP, which acts as an agonist for the STING (stimulator of interferon genes) receptor, leading to induction of a type I interferon response. 

cGAS STING Pathway

Accurate Dose Response Measurements

DRC using known inhibitors, G150. Here, we used 100 μM ATP, 100 μM GTP, 100 nM ISDNA, 20 mM Tris (pH 7.5), 5 mM MgCl2, & 0.01% Brij-35 (pH 7.5). The Detection Mix included 1X Stop & Detect Buffer C, 16 nM ATTO 647 Tracer, & 8 nm cGAMP Antibody-Terbium.

cGAS Assay DRC with G150 inhibitor in TR-FRET Readout

IC50 [G150] = 0.05 μM

Far-Red TR-FRET Readouts Validated on Major Multimode Readers

SupplierInstrumentTR-FRET Assays
TriStar2S LB 942Click Me ArrowValidated
Tristar 5In Review
Mithras2 LB 943Click Me ArrowValidated
CytationTM 5Validated
CytationTM 3Validated
CytationTM 1Validated
SynergyTM H1Validated
SynergyTM 2/H4/4Click Me ArrowValidated
SynergyTM HTXNot Capable
SynergyTM Neo 2Validated
POLARstar® OmegaClick Me ArrowValidated
FLUOstar® OmegaClick Me ArrowValidated
PHERAstar® FSXClick Me ArrowValidated
PHERAstar® Plus/FSClick Me ArrowValidated
CLARIOstar® /PlusClick Me ArrowValidated
VANTAstarTMClick Me ArrowValidated
SenseIn Review
Analyst® GT/HTClick Me ArrowValidated
Gemini® XPS/EMNot Capable
SpectraMax® M2/M2eNot Capable
SpectraMax® M5/M5e/FlexStation® 3Click Me ArrowValidated
SpectraMax® ParadigmClick Me ArrowContact Us
SpectraMax® iD3/iD5Click Me ArrowValidated
SpectraMax® i3xClick Me ArrowValidated
EnVision®/EnVision® XciteClick Me ArrowValidated
Infinite® M1000/M1000Pro/Safire2TMClick Me ArrowValidated
Infinite® M200Not Capable
Infinite® F500Click Me ArrowValidated
Infinite® F200/UltraevolutionClick Me ArrowContact Us
SparkTM 10MClick Me ArrowValidated

Validation Criteria for Plate Readers

  • 384-Well Format
  • Z'-Factor ≥ 0.7 at 10% conversion of 10 μM ATP
  • Z' specifications to be met using Transcreener ADP2 Assay Reagents
  • Read time to achieve Z' specifications ≤ 5 minutes

Look for these stickers on instruments that have successfully met the validation criteria.

The instrument validation program is a collaborative effort with the major suppliers of multimode readers to insure that Transcreener assays perform optimally on your specific instrument. Scientists at BellBrook and/or the instrument vendor have tested Transcreener reagents with each instrument to determine optimal filters and settings for maximal assay performance. We provide you with application notes with all the important details, so you can be confident of success using Transcreener assays on the instrument of your choice. 

What's Included

What You Will Need

Transcreener cGAMP Assay Kits - TR-FRET Readout

* For custom or bulk orders (over 100,000 wells) please contact us (info@bellbrooklabs.com) for a quote.

cGAS Screening Bundles - TR-FRET Readout

* Includes enough enzyme for respective wells when used at 1.75 μg/mL (30 nM)

Assay Plates for TR-FRET

cGAS Enzyme Ordering Information

* For custom or bulk orders (over 100 μg) please contact us (info@bellbrooklabs.com) for a quote.