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  • There are other, higher levels of regulation that occur here

  • and I started to talk about them when I mentioned our

  • RB protein. So, control of the cell cycle

  • occurs on a higher level with a couple of

  • key proteins in addition to RB.

  • One of the main proteins we talk about that

  • regulate on a very high level is p53.

  • It's even got a nickname: it's the "guardian of the genome."

  • It's so important, actually, that Science Magazine called it,

  • "the molecule of the year" in 1993.

  • Theobromine, the main molecule that's in chocolate,

  • hasn't even gotten this honor yet. So it shows you

  • how important p53 is. It's more important than chocolate.

  • P53 will bind DNA directly to produce proteins that block

  • the progression of the cell cycle.

  • One of those proteins include p21.

  • P21 will function to inhibit CDK.

  • So the CDK will not be able to activate

  • DNA replication or activate mitosis.

  • RB is another protein that is associated

  • with the function of P53, and these proteins are considered

  • tumor suppressor genes, so RB is a protein that is

  • produced from a tumor suppressor gene, just like p53,

  • so I'll write that down here. These proteins are considered

  • tumor suppressor genes... They're made from

  • tumor suppressor genes I should rather say.

  • These proteins are made from tumor suppressor genes,

  • which are important to have because

  • if they are defected, or if they have a mutation in them

  • that makes them have loss of function,

  • so that's an important term,

  • (repeats) defected or if they have a loss of function,

  • what ends up happening is that you tend to get cancer.

  • Cancer, which I think you and I can both agree is not

  • a good thing to have. So, it is very important

  • to have tumor suppressor genes.

  • To illustrate how important that is, if you look at

  • p53, greater than 50% of tumors have a defect in p53.

  • RB got its name because a defect in RB would lead to a

  • tumor of the eye, known as retino-that's where you got the R-

  • retinoblastoma, which is why these two proteins are

  • considered tumor suppressor genes.

  • P21 is very unusual in that it doesn't actually lead to

  • cancer when it's defected. Instead,

  • scientists have found that mice that are without p21

  • have the ability to regenerate their limbs.

  • How weird is that?!

  • P21 lack causes the ability to regenerate their limbs,

  • their arms and legs.

  • So we're all still trying to figure out exactly

  • how some of these key proteins work.

  • But it's important to understand that

  • these tumor suppressor genes

  • are essential for making sure that we regulate

  • the cell cycle so we don't just go to the

  • divide, divide, divide phase.

  • We want to make sure that we only divide when it's appropriate,

  • when a cell is ready to, or if it's even a cell that

  • is supposed to divide in the first place.

  • Because, as we'll see in our next couple of videos,

  • mitosis, or cell division, requires a lot of energy

  • and protein machinery to happen.

  • So we need to make sure it's the right time to divide.

There are other, higher levels of regulation that occur here


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B1 中級

癌症中細胞週期控制的喪失 (Loss of Cell Cycle Control in Cancer)

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    Study English 發佈於 2021 年 01 月 14 日