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P53 Gene

by Georgina Cornwall, PhD
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    00:00 So the question is what happens when the cell cycle controls are broken? You're probably familiar with the idea that cancer results from uncontrolled cell division.

    00:13 It's sort of like having a stucked gas pedal or a broken break pedal.

    00:18 So one of the genes that's of particular interest is the p53 gene because it turns out it shows up in quite a lot of cancers.

    00:27 The p53 gene is going to play a role in the G1S checkpoint, so the checkpoint between growth phase 1 and synthesis.

    00:39 And the role that it plays is in checking that DNA is in good structure before we go through synthesis, so checking for errors If there are errors, the p53 enzyme will correct those errors. Sometimes the errors might be too big to correct in which case the p53 enzyme does its job and says "You know what, this is way too much for me to handle, we cannot let the cell divide". So the p53 enzyme will destroy those cells, so that they don't further their damage and move on into the cell cycle. So this is a great example of one of the proteins that's involved in the G1S checkpoint.

    01:26 So in this case, p53 is considered a tumor suppressor gene. In its normal form, it suppresses the growth of tumors because it's checking the DNA and if things aren't right, then we kill the cell, it's all over, that cell is not going to divide.

    01:46 Only cells that are in good working order would be allowed to go into S phase.

    01:52 So many cancers have a broken p53 gene which means it produces a non functional p53 protein.

    02:05 With the non functional p53 protein, we don't get the DNA checking that we should get.

    02:12 And so what happens is there is no stop to cell division and no DNA repair.

    02:19 And if there is an error, there's nothing to stop the cells from dividing.

    02:24 And if we have enough errors developing in a particular cell through certain rounds of cell division, then this could develop into a cancer. So essentially here, we have a gas pedal that's on, or a lack of a break pedal, right.

    02:40 No break to slow it down, fix the repairs, and make sure that unworthy cells don't move forward.

    02:48 So p53 is a very important protein involved in cell cycle control.


    About the Lecture

    The lecture P53 Gene by Georgina Cornwall, PhD is from the course Cell Cycle and Cell Division.


    Included Quiz Questions

    1. …the formation of tumors due to continuous cell division of the mutated cells.
    2. …the repair of the mutated p53 gene.
    3. …the activation of cell destruction mechanisms.
    4. …the activation of cell division pausing genes.
    5. …the suppression of replication of DNA.

    Author of lecture P53 Gene

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD


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    More info needed
    By Andrey K. on 30. May 2018 for P53 Gene

    Nothing on how p53 relates to RB or how p53 induces p21 to inhibit CDK thus acting as a tumor suppressor by not allowing cell cycle progression. This info is found in the the First Aid for the USMLE so it is probably important.