7. Proto-oncogenes and Oncogenes

hello and welcome back to oncology for medical students in this section of videos on the molecular basis of cancer this video will cover proto-oncogenes and oncogenes in the previous videos we talked about how cancers develop as a result of mutations to DNA how these changes lead to the production of faulty proteins and how these proteins give the cells certain characteristics known as the hallmarks of cancer we've also talked about how the genes involved in these changes can also be divided into two groups tumor suppressor genes covered in the last video and proto-oncogenes cells contain many genes that produce proteins that encourage the cell to move through the cell cycle and divide the normal forms of these genes are called pro so oncogenes when they mutate way that they are active all the time they promote cell division on the development of cancer the mutated forms of these genes are called oncogenes where tumor suppressor genes stop the cells moving through the cell cycle like the brakes of a car oncogenes are like the accelerator pedal where a loss of function of tumor suppressor genes promote the growth of cancer it's a gain in function of proton code genes turning them into oncogenes that Leeson leads to the growth of cancers because we have two copies of each gene to stop a gene from producing a properly functional protein both copies have to be taken out this type of loss of function applies to tumor suppressor genes but this isn't the case with oncogenes because we're talking about genes that gainer function it's only necessary for one copy to become mutated to promote the growth of cancer the most commonly mutated oncogene in human cancers is the rats on coaching to see how it functions again we'll have to have a look inside the cell in normal cells in its inactive state the Rass protein is bound to a molecule called gdp guanosine diphosphate in order to become active the Rass gene must substitute the gdp molecule for another GTP guanosine triphosphate this happens by the action of a protein called a guanosine triphosphate or GTP exchange factor this type of protein exchanges the gdp on the inactive rass protein for a gtp which activates the wrasse protein Russ then in turn activates a number of transcription factors that lead to the activation of genes involved in progressing through the cell cycle and dividing you the wrasse protein then deactivates by the action of something called gtp A's activity this means it breaks down the gtp to GDP it does this with the help of a protein called a GTP A's accelerating protein or gap the inactivation is very important it provides a way of controlling the rats activity and therefore controlling self growth and division if the portion of the wrasse protein responsible for the gtp A's activity mutates it may not be able to break down the gtp this means that the gtp is stuck bound to the wrasse protein and it's permanently active leading to uncontrolled cell division because the mutation is leading to a gain of function only one copy of the gene needs to mutate to causes to happen now that will cover both tumor suppressor genes and oncogenes I thought would finish with a quick comparison where tumor suppressor genes are involved in preventing cell growth and division proto-oncogenes or the mutated counterparts oncogenes promote cell growth and division it's normally a loss of function of tumor suppressor genes that leads to the development of cancers whereas on the other hand with uncle genes it's a gain of function to use the car analogy the tumor suppressor genes are like the car breaks on the cell cycle and the onion the case of oncogenes they like the car accelerator because we have two copies of each gene and the case of tumor suppressor genes you need both copies to be taken out to lead to the development of cancer so they need two hits and the case of oncogenes they just need one mutation thank you

Channel: Oncology for Medical Students

Views: 177,813

Keywords: oncology, medical, students, med, RAS, GEF, oncogene, proto, proto-oncogene, oncogenes, tumour, suppressor, genes, cell cycle, transcription factor, hallmarks, of, cancer

Id: 9J8cMW94VUs

Length: 5min 22sec (322 seconds)

Published: Sun May 08 2016