According to molecular biology, reporter genes are genes that have been inserted into the regulatory sequences of other genes of interest in microbes, cell cultures, animals, or plants. They are also known as pure sensor genes. 

These genes are called “reporters” because the traits they bestow on the organisms that express them are simple to measure and identify. Additionally, they can serve as markers. Reporter genes are frequently employed to demonstrate the integration or expression of genes in cells or other creatures.

A reporter protein is easy to find and not typically found in your research system. For instance, if you were researching bacteria, you wouldn’t want to use a bacterial protein as your reporter. There are numerous reporter proteins in use, including -galactosidase (encoded by the bacterial gene lacZ), luciferase, chloramphenyl acetyltransferase (CAT), GUS (-glucuronidase), which is frequently used in plants, and green fluorescent protein (GFP; from jellyfish).

The bacterial gene lacZ encodes β-galactosidase, which is still one of the most well-known sensor proteins. Lactose, a milk sugar disaccharide, is broken down by bacteria’s  β-galactosidase enzyme into glucose and galactose. The colorless precursor X-gal (5-bromo-4-chloro-3-indolyl-galactopyranoside) is broken down by the enzyme β-galactosidase into galactose and an insoluble blue product. Since lacZ is not present on the majority of chromosomes, it can be used as a reporter gene (for example, the blue/white selection).

The Most Common Reporter Genes

A reporter gene is introduced into an organism by combining it with a gene of interest in the DNA construct that will be introduced into the cell or organism.

This typically takes the shape of a plasmid, a circular DNA molecule present in prokaryotic or bacterium cells in culture. This is called a viral host for viruses. Since the expression of the reporter gene is used as a marker for the successful uptake of the gene of interest, it is crucial to use a reporter gene that is not naturally expressed in the cell or organism being studied.

Fluorescent and luminescent proteins are used as reporter genes that produce visibly recognisable characteristics. Examples include the enzyme luciferase, which catalyzes a reaction with luciferin to create light, the jellyfish green fluorescent protein (GFP) gene, which causes cells that express it to glow green under blue light, and the red fluorescent protein from the gene DSRed. Plants traditionally use the GUS gene, but Luciferase and GFP are increasingly employed.

The E. coli lacZ gene, which produces beta-galactosidase, is a frequent sensor in bacteria. When grown on a medium containing the substrate analogue X-gal, this enzyme makes bacteria expressing the gene look blue. The chloramphenicol acetyltransferase (CAT) gene, which gives resistance to the antibiotic chloramphenicol, is an example of a selectable marker that is also a reporter in bacteria.

Transformation and Transfection Assays

Many transfection and transformation techniques, which are two ways to express a foreign or modified gene in an organism, only work in a tiny proportion of the population. Therefore, a technique for locating those few instances of effective gene uptake is required. The reporter gene can be expressed constitutively (that is, it is “always on”) or inducibly with an outside intervention, such as the addition of Isopropyl-D-1-thiogalactopyranoside (IPTG) in the beta galactosidase system. An RG can be expressed under its own promoter when used in this manner, independent of the gene it is inserted into. 

As a consequence, the reporter gene’s expression is unrelated to the gene of interest’s expression. This is advantageous when the gene of interest is expressed only under particular circumstances or in difficult-access tissues.

Gene Expression Assays

A gene of interest whose transcript is typically challenging to quantify can be tested using reporter genes. RGs can create a protein that has little immediate or apparent impact on the cell culture or organism. Reporter genes should be absent from the native genome in order to isolate the expression of the gene of interest. 

Novel coincidence reporter designs with artefact suppression have been created because reporter enzymes (like firefly luciferase) can be direct targets of small molecules and confuse HTS data analysis. In order to find small molecule inhibitors and activators of protein targets and pathways for drug development and chemical biology, high throughput screening (HTS) uses reporter gene assays. 

This article, A Brief Guide to Reporter Proteins, was written to pique your interest and get you familiar with the topic. If you would like to receive more information or to shop reporter proteins at Pharna.com to be the first to know what is new.