NanoLuc® luciferase has been discussed many times on this blog and our web site because the enzyme is integral to studying genetic responses and protein dynamics. While NanoLuc® luciferase was first introduced as a reporter enzyme to assess promoter activity, its capabilities have expanded far beyond a genetic reporter, creating tools used to study endogeneous protein interactions, target engagement, protein degradation and more. So where did the NanoLuc® luciferase come from and how does a one enzyme power several technologies?Continue reading “NanoLuc® Luciferase Powers More than Reporter Assays”
The ability to target protein interactions with low solubility or weak binding affinities can present a significant challenge when it comes to drug screening. The beauty of these types of challenges we often face in the lab is that finding solutions to these problems doesn’t necessarily require brand new tools. Sometimes we already have the right tools in our arsenal and, with just a little creativity and collaboration, they can be adapted to address the challenge at hand.
In the following video, Dr. Mohamed (Soly) Ismail, a Postdoctoral Fellow at the Downward Lab of the Francis Crick Institute, presents the perfect example of this with his novel approach to the NanoBiT® Protein:Protein Interaction Assay. Through a collaboration with Promega R&D Scientists, Dr. Ismail has translated the assay into a cell-free, biochemical format, termed the NanoBiT Biochemical Assay (NBBA).Continue reading “From Live Cells to Lysates: Adapting NanoBiT to a Biochemical Assay Format”
Remdesivir (RDV or GS-5734) was used in the treatment of the first case of the SARS-CoV-2 (formerly 2019-nCoV ) in the United States (1). RDV is not an approved drug in any country but has been requested by a number of agencies worldwide to help combat the SARS-CoV-2 virus (2). RDV is an adenine nucleotide monophosphate analog demonstrated to inhibit Ebola virus replication (3). RDV is bioactivated to the triphosphate form within cells and acts as an alternative substrate for the replication-necessary RNA dependent RNA polymerase (RdRp). Incorporation of the analog results in early termination of the primer extension product resulting in the inhibition.
Why all the interest in RDV as a treatment for SARS-CoV-2 ? Much of the interest in RDV is due to a series of studies performed by collaborating groups at the University of North Carolina Chapel Hill (Ralph S. Baric’s lab) and Vanderbilit University Medical Center (Mark R. Denison’s lab) in collaboration with Gilead Sciences.Continue reading “Investigation of Remdesivir as a Possible Treatment for SARS-2-CoV (2019-nCoV)”
Bioluminescent reporter assays are an excellent choice for analyzing gene regulation because they provide higher sensitivity, wider dynamic range and better signal-to-background ratios compared to colorimetric or fluorescent assays. In a typical genetic reporter assay, cells are transfected with a vector that contains the sequence of interest cloned upstream of a reporter gene, and the reporter activity is used to determine how the target sequence influences gene expression under experimental conditions. A second control reporter encoded on the same or a different plasmid is an essential internal control. The secondary reporter is used to normalize the data and compensate for variability caused by differences in cell number, lysis efficiency, cell viability, transfection efficiency, temperature, and measurement time.
For genetic reporter assays, using a secondary control vector with a weak promoter like PGK or TK to ensures that the control does not interfere with activation of your primary reporter vector. Transfection of high amounts of the control plasmid or putting the control reporter under control of a strong promoter like CMV or SV40 often leads to transcriptional squelching or other interference with the experimental promoter (i.e., trans effects). Reporter assays can also be used to quantitatively evaluate microRNA activity by inserting miRNA target sites downstream or 3´ of the reporter gene. For example, the pmirGLO Dual-Luciferase miRNA Target Expression Vector is based on dual-luciferase technology, with firefly luciferase as the primary reporter to monitor mRNA regulation and Renilla luciferase as a control reporter for normalization.
Here in Technical Services we often talk with researchers who are just starting their project and looking for advice on designing their genetic reporter vector. They have questions like:
- How much of the upstream promoter region should be included in the vector?
- How many copies of a response element will be needed to provide a good response?
- Does the location of the element or surrounding sequence alter gene regulation?
You have identified and cloned your protein of interest, but you want to explore its function. A protein fusion tag might help with your investigation. However, choosing a tag for your protein depends on what experiments you are planning. Do you want to purify the protein? Would you like to identify interacting proteins by performing pull-down assays? Are you interested in examining the endogenous biology of the protein? Here we cover the advantages and disadvantages of some protein tags to help you select the one that best suits your needs.
The most commonly used protein tags fall under the category of affinity tags. This means that the tag binds to another molecule or metal ion, making it easy to purify or pull down your protein of interest. In all cases, the tag will be fused to your protein of interest at either the amino (N) or carboxy (C) terminus by cloning into an expression vector. This protein fusion can then be expressed in cells or cell-free systems, depending on the promoter the vector contains. Continue reading “Choosing a Tag for Your Protein”
Cardiovascular diseases, or CVDs, are collectively the most notorious gang of cold-blooded killers threatening human lives today. These unforgiving villains, including the likes of coronary heart disease, cerebrovascular disease and pulmonary embolisms, are jointly responsible for more deaths per year than any other source, securing their seat as the number one cause of human mortality on a global scale.
One of the trademarks of most CVDs is the thickening and stiffening of the arteries, a condition known as atherosclerosis. Atherosclerosis is characterized by the accumulation of cholesterol, fats and other substances, which together form plaques in and on the artery walls. These plaques clog or narrow your arteries until they completely block the flow of blood, and can no longer supply sufficient blood to your tissues and organs. Or the plaques can burst, setting off a disastrous chain reaction that begins with a blood clot, and often ends with a heart attack or stroke.
Given the global prevalence and magnitude of this problem, there is a significant and urgent demand for better ways to treat CVDs. In a recent study published in Nature Communications, researchers at the Carnegie Institution for Science, Johns Hopkins University and Mayo Clinic are taking the fight to CVDs through the study of low-density lipoproteins (LDLs), the particles responsible for shuttling bad cholesterol throughout the bloodstream.Continue reading “Striking Fear into the Heart of Cardiovascular Disease Using Zebrafish and NanoLuc® Luciferase”
G Protein-Coupled Receptors (GPCRs) are a very large, diverse family of transmembrane receptors in eukaryotes. These receptors detect molecules outside the cell and activate internal signaling pathways by coupling with G proteins. Once a GPCR is activated, β-arrestins translocate to the cell membrane and bind to the occupied receptor, uncoupling it from G proteins and promoting its internalization.
Reporter tags are useful for studying the dynamics of GPCRs and associated proteins, but large tags can disrupt the receptors’ native functioning, and often overexpression of the tagged protein is required to obtain sufficient signal. Here is one example of how researchers have used the small, bright NanoLuc® luciferase to overcome these common challenges and answer questions about GPCRs. Continue reading “Lighting Up GPCR Research with Bioluminescent Tagging”
It’s a question I’m asked probably once a week. “What wavelength do I select on my luminometer when performing a luciferase assay?” The question is a good and not altogether unexpected one, especially for those new to bioluminescent assays. The answer is that in most cases, you don’t and in fact shouldn’t select a wavelength (the exception to this rule is if you’re measuring light emitted in two simultaneous luciferase reactions). To understand why requires a bit of an explanation of absorbance, fluorescence, and luminescence assays, and the differences among them.
Absorbance, fluorescence, and luminescence assays are all means to quantify something of interest, be that a genetic reporter, cell viability, cytotoxicity, apoptosis, or other markers. In principle, they are all similar. For example, a genetic reporter assay is an indicator of gene expression. The promoter of a gene of interest can be cloned upstream of a reporter such as β-galactosidase, GFP, or firefly luciferase. The amount of each of these reporters that is transcribed into mRNA and translated into protein by the cell is indicative of the endogenous expression of the gene of interest. Continue reading “Why You Don’t Need to Select a Wavelength for a Luciferase Assay”
No protein is an island. Within a cell, protein-protein interactions (PPIs) are involved in highly regulated and specific pathways that control gene expression and cell signaling. The disruption of PPIs can lead to a variety of disease states, including cancer.
Two general approaches are commonly used to study PPIs. Real-time assays measure PPI activity in live cells using fluorescent or luminescent tags. A second approach includes methods that measure a specific PPI “after the fact”; popular examples include a reporter system, such as the classic yeast two-hybrid system.
Malaria affects nearly half of the world’s population, with almost 80% of cases in sub-Saharan Africa and India. While there have been many strides in education and prevention campaigns over the last 30 years, there were over 200 million cases documented in 2017 with over 400,000 deaths, and the majority were young children. Despite being preventable and treatable, malaria continues to thrive in areas that are high risk for transmission. Recently, clinicians started rolling out use of the first approved vaccine, though clinical trials showed it is only about 30% effective. Meanwhile, researchers must continue to focus on innovative efforts to improve diagnostics, treatment and prevention to reduce the burden in these areas.