Back in 2007
, scientists were able to turn skin cells into iPS cells by adding four genes. But the genes didn't do the actual magic. Instead, it was the proteins that came from the genes' instructions that transformed the cells.
Each gene has the instructions for making a specific protein. And that specific protein goes on to do a specific job in the cell.
For example, the HBB gene has the instructions for making hemoglobin. And hemoglobin's job is to carry oxygen in our blood.
The four genes that turned cells into iPS cells were Oct4, Sox2, Klf4, and c-Myc. These genes have the instructions for making proteins with the same names. It is these four proteins and not the genes that did the actual work of turning a skin cell into an ES cell.
So it makes sense that just adding the proteins themselves should be able to transform the cells. But why would any scientist want to do this if genes work? Because adding a protein is safer.
Why Adding Proteins is Safer than Adding Genes
At first blush, it might seem odd that genes are more or less safe to add to a cell than the proteins they produce. But genes are more dangerous.
When a scientist adds a gene to a cell, it can sometimes turn on other genes. And those other genes can sometimes cause the cell to turn cancerous.
Genes are stored in
chromosomes like these.
A cell's genes are stored in long DNA structures called chromosomes. When a gene is added, it sticks itself into one or more of these chromosomes. If the added gene lands near another gene, it can affect how that nearby gene works.
The nearby gene might now cause the cell to grow uncontrollably or make the cell refuse to die. In other words, the added gene might cause the nearby gene to turn the cell into a cancer cell.
The second problem has to do with how long a protein is around. In this case, scientists want the proteins to be there just long enough to do their job. This is because these proteins can sometimes cause cancer by themselves if they are around too long.
Since most proteins wear out pretty quickly, this shouldn't be a problem. Unless the protein's gene is there to replace worn out copies of the protein. When this happens, working protein can stay around for a very long time.
This is exactly what happens when genes are added to a cell. The added gene often just keeps making protein long after the protein is still needed.
But if scientists add just the protein, then when it wears out, it won't be replaced. So adding just the proteins to the cell is safer. Unfortunately, adding a protein is not easy.