What is gene expression and why should we care?
Surface level, the concept's as simple as turning a lightbulb on with a flick of a switch. But unlike lightbulbs, gene expression is the key to maintaining the precarious balance of RNA, enzymes, and other cellular machinery deep within us.
So what exactly is gene expression?
"Gene expression is the process by which the information encoded in a gene is turned into a function" (genome.gov).
In short, gene expression determines which of your genes are “turned” on/off, and if it will fulfill its specific task.
Gene Expression: Explained
Genes are the very basis of who we are. Their genetic code is “read” by the cell, and serves as instructions by which the cell follows.
Usually, a protein called a repressor will bind to the gene(s), turning it “off”. Until the repressor is unbound, the gene(s) cannot be expressed. Whether the repressor binds to the gene depends on many internal and external factors.
In many catabolic pathways, where the cell breaks down nutrients into simpler molecules, the repressor’s natural state is to be active. It can freely suppress the genes it matches to. This makes sense because it prevents the cell working to break down nutrients that aren’t even there, wasting energy in the process. On the other hand, when nutrients enter the cell, small molecules called inducers bind to the repressors, preventing the repressors from suppressing the genes. The genes are now NOT repressed, letting the cell break down the newly-arrived nutrients into their smaller components. This process is a type of negative gene regulation, or inducible gene expression.
On the flip side is repressible gene expression. The process is almost the same, with the difference being that the repressor starts out as inactive. This version of gene expression is mostly used for the synthesis of crucial molecules from smaller materials. In this case, the cell is free to make essential molecules from the continuous stream of nutrients that enter our body. Once the cell has made too much of a specific molecule, the repressor activates and binds to the gene, immediately halting production. By doing this, the cell can avoid wasting materials on a product which it already has enough, and in turn spend those materials on making other products.
Another type is positive gene regulation. This increases production of a protein when needed. In addition to the usual repressor, which has a specific molecule bound to it (and therefore suppressing it), another molecule binds to the promoter. This activates the gene and lets it perform its specific function.
Why should we care?
Manipulating gene expression is an important part of gene therapy. Using different techniques we can turn on genes to combat diseases, or turn off malfunctioning genes. Gene therapy is actively being researched to treat not only genetic disease, but cancer and infectious diseases too. The first gene therapy was in 1990, but we are still learning about what it can truly accomplish.
References
Brody, Lawrence. "Gene Expression." National Human Genome Research Institute, National Institutes of Health, 23 Aug. 2023, www.genome.gov/genetics-glossary/Gene-
Expression. Accessed 24 Aug. 2023.
Campbell, Neil A. Biology: A Global Approach. Global ed., Harlow, Pearson, 2021.
"What Is Gene Therapy?" MedlinePlus, National Institutes of Health, 28 Feb. 2022, medlineplus.gov/genetics/understanding/therapy/genetherapy/. Accessed 24 Aug. 2023.