Action of Transcriptional Regulators

Hi in this video, I'm gonna be talking about the action of transcription regulators. So the first kind of action that I want to talk about is the fact that transcription regulators work in combination with other proteins. Now I've already mentioned this in previous videos but I really just want to add an extra layer of what I mean and how this whole entire process works. So combinations of regulator proteins work together to regulate or control whichever one you prefer gene expression. So what this means is multiple proteins work together to control the expression of a single gene. So usually how this works is there's a single protein that binds first and this protein has a really high affinity or sort of bind strongly to whatever element it's binding to. And then this finding sort of changes confirmations or recruits other proteins and increases the affinity of all of these other proteins that as they get added on sort of bind more strongly and um really the function this is to limit the number of transcription regulators needed because if they all sort of bind bound very weakly you would need a lot of them to exert some kind of function. Whereas if the affinity is constantly being increased with each one, their binding strongly they can have a stronger function. However expression can be decided by single regulatory protein, meaning that this would be kind of like an on off switch. So you have say 20 proteins there and the 21st one is really what pushes it to stimulate. So if you never get the 24 First one protein to get to the correct area or bind to the correct things, then even if all other 20 proteins are there and ready to go, it needs the 21st to really get started. So turn that switch on and on and off switch. Now The same combinations can control the generation of different cell types. So there are a few transcription factors or transcription regulators that control sets of genes involved in cell differentiation. So you say you have your 20 gene regulators and they are all responsible for creating a kidney cell. And so the all these regulators all control all the genes or most of the genes responsible for differentiating a cell into a kidney cell. So combinations can work on different genes. It's not just every gene has a different combination but sets of genes can have similar ones, especially that result in cell differentiation. Um and then also combinations can be controlled by environmental signals. So response elements for instance our D. N. A sequences and a promoter that bind to regulatory proteins. But response elements binds a regulatory proteins that are stimulated by kind of external signals. So for instance you might read about heat shock response elements but respond when the cell is in temperatures that are really high or different hormones act this way. So hormone signals can activate response elements. And so these are all external signals that can work to regulate the transcription of a gene. So here we have an example of sort of combinations You have your RNA Plymouth race, You have your promoter region here, you can kind of see this little green, you have all these different regulators and to all that all support and work together to support the transcription of a gene. So combinations are really important. So now let's move on.

So in this video I'm going to be walking through the steps of gene activation. So remember cell biology likes to do a lot of different steps. We're going to be memorizing a lot of steps, a lot of pathways. And so this is the pathway for gene activation. So first so what happens is regulatory proteins bind to an enhancer and then this binding stimulates the D. N. A. To form a loop which connects the enhancer and the promoter. Once the enhancer and promoter are together, activators come in, interact with co activators to alter chromosome structure. The chromosome structure allows for loosening of the chroma tin. And these activators also interact with a protein known as a mediator. And the mediator facilitates the correct positioning of RNA polymerase and then RNA polymerase can start transcribing. So we're looking at what this looks like. I've sort of notated here each step. So in step one the enhancer is bound and step to this sort of recruits this loop here where the enhancer and the promoter can interact in step three different types of other activators are recruited. Step four is when the mediator helps facilitate the interaction between these activators and RNA plum Race. RNA collaborates. Thing comes in. Um And then finally in step six the gene is transcribed. So those are the six steps to gene activation. So now let's move on

So in this video I'm going to be talking about a really important class of transcription regulators and that is nuclear receptors. And nuclear receptors are transcription regulators that are responsible for sensing hormones. Things like steroids and then rigging regulating gene expression based on hormones. So nuclear receptors contain a few important structures so one is that there's an in terminal domain um and this is a sort of an activation domain, This is really what's activated by the hormone and then there's a second structure, a DNA binding domain which is going to interact with the D. N. A. And then support some type of transcription regulation. So nuclear receptors also have things known as inverted repeats which are sequences of nucleotides um that are followed downstream of of something down later downstream by kind of a reverse compliment. So reverse compliment. It's kind of a fancy term that we use in genetics a lot to actually talk about the sequence of the gene. Um but the inverted repeat is exactly what it sounds like. It's just kind of a reverse of a reverse sequence of the one upstream nuclear receptors contain a lot of these and the nuclear receptor itself binds a region of DNA called the hormone response elements. So these are going to be inverted repeats that many nuclear receptors find. So here's an example of hormone activation. Now there's a lot of fancy things here, you don't need to know about. Just realize that outside of here is the side of plasm and inside is the nucleus but not a cell, it's a nucleus and we have our hormone here that enters into the cell, interacts with a variety of things To activate transcription. And transcription eventually results in the development of a protein and some kind of change cell function in response to the hormone itself. So this is how hormones work. So now let's move on.