Our next process to discuss is that of transcription. And as a reminder, transcription is the process by which the information stored in a strand of DNA is copied into messenger RNA. And the storing of information in this manner allows for stability of the genetic material because changes to DNA are not common. Transcription also produces ribosomal RNA and also transfer RNAs. Transcription involves this enzyme RNA polymerase and this enzyme adds bases similar to DNA polymerase to the 3'-OH.
We're going to come back and talk about the actual process here in a moment. Now RNA polymerase contacts many bases of the DNA simultaneously so it has certain subunits, it's a hollow enzyme again, it has certain subunits that are going to allow it to do certain things in this process of transcription. So we're going to go through a few of these. And I just want to point out here that we're seeing bacterial RNA polymerase, which is the simplest structure. Archaea and Eukaryote have similar structures, but the process is a little bit more complicated, and we're not going to go into those processes in this class.
So in bacteria, there are five different subunits in the RNA polymerase holoenzyme. And these are, we've got beta that we see here, we got beta prime that we see here, we've got alpha, omega, and sigma, which is not drawn on here. And sigma pretty much kind of sits here. Okay, we'll draw that on temporarily. Alpha and omega here, these two will assemble the complex, which can then be loaded and bound to the major groove of the DNA by alpha.
They're later held there by beta and beta prime. So we'll come back to those later about how that all works. Right now, we're just going to say that assembly occurs with alpha and omega. And you do not need to know these subunits.
I just want you to know that there are two subunits. involved in assembly and then DNA binding also includes a number of subunits. Now the ones I do need you to know about are these two here beta and beta prime because these are the ones that are actually involved in the process of RNA synthesis. So these two together form like a giant hand that will allow the interactions to occur between the DNA molecule and the newly formed RNA molecule.
Come back to that process here in a moment. The other one that you're going to become very familiar with is the sigma factor, which recognizes the promoter, which allows us to know which part of the DNA are we going to copy. And we'll come back and talk about some of these here in a moment. Unlike DNA polymerase that needed a primer, RNA polymerase needs no primer. The RNA polymerase holoenzyme will...
bind loosely to a major groove in the DNA. So this will bind to a major groove in the DNA. And as a reminder, it's the alpha subunit.
So part of the hollow enzyme will bind. It's not the whole enzyme. It's just a part of the enzyme will bind, but it binds loosely.
It's not bind very tightly just yet. What will happen is this is considered to be closed and I'll explain what an open complexes in a moment and that will make this easier to understand but what's happening is it's bound loosely so that it's able to travel down the DNA molecule to find and identify a promoter region which I will describe here in a moment and that is happening because the sigma factor is currently attached to this complex. So this complex this closed complex is traveling down the DNA looking for a particular promoter region for transcription to begin.