Normal Cell Division: Gene Transcription and Mitosis Induction

00:00 Okay, we're going to move on now and talk about normal cell division because you have to understand kind of the normal cell pathways that are going to drive cellular proliferation so that we can understand what goes wrong when we have loss of tumor suppressors or expansion of oncogenes. So in a normal cell, this is a schematic where a growth factor is coming in, it is going to bind to and dimerize proteins that are in the membrane. This is just an example of a kinase, a tyrosine kinase activated receptor. This is a receptor that's going to have intrinsic tyrosine kinase activity. So that growth factor comes in, it binds and when it binds by bringing those 2 halves of the receptor together, they now autophosphorylate each other. Okay. We've changed the confirmation of the protein and now they acquired those little piece, they've got to have phosphorylation. That's now an active kinase by virtue of the phosphorylation. And that active kinase will now phosphorylate a whole bunch of other proteins. And again, I'm specifically not going in to the details because it's a little bit different for every cell type and every cancer, everything. So, basically you have growth factor that normally activates the receptors and then that will phosphorylate additional proteins and in a cascade of phosphorylation we'll eventually get something that is able to access the nucleus, a transcription factor that's become phosphorylated that can now sit down on its appropriate promoter site and cause the transcription of new nuclear material, of new message to drive whatever process we're going to drive. That's the normal kind of pathway. With the gene transcription, then we can talk about proliferation, we can talk about making new elements, we can talk about acquiring some of the other features of a proliferating cell. That gets us into the normal mitotic pathway and in subsequent talks we will talk about how this goes wrong in malignancy. And with that, I conclude.