RNAi: Slicing, dicing and serving your cells - Alex Dainis

譯者: CPR weng 審譯者: Regina Chu

You can think of your cells

你可以把細胞比擬為

as the kitchen in a busy restaurant.

忙碌的餐廳廚房

Sometimes your body orders chicken.

有時候身體會點雞排

Other times, it orders steak.

有時則要一份牛排

Your cells have to be able to crank out

你的細胞需要去製造

whatever the body needs

身體的需求

and quickly.

而且要很快

When an order comes in,

得到點單後

the chef looks to the cookbook, your DNA,

主廚會看看烹飪書：也就是 DNA

for the recipe.

尋找配方

She then transcribes that message

然後，它抄寫（轉錄）配方

onto a piece of paper called RNA

到一張紙上，就是所謂的 RNA

and brings it back to her countertop, the ribosome.

並把它帶回流理台，核糖體。

There, she can translate the recipe into a meal,

接著，它可以把這些食譜翻譯成食物

or for your cells, a protein,

就是身體細胞所需的蛋白質

by following the directions that she's copied down.

按著步驟做出大餐

But RNA does more for the cell

但是 RNA 的功能

than just act as a messenger

不是只在廚師和食譜之間

between a cook and her cookbook.

傳遞訊息而已。

It can move in reverse and create DNA,

它還能反過來合成 DNA

it can direct amino acids to their targets,

引導胺基酸至特定地方

or it can take part in RNA interference,

或是進行 RNA 干擾

or RNAi.

簡稱 RNAi

But wait!

等等！

Why would RNA want to interfere with itself?

為什麼 RNA 要干擾自己呢？

Well, sometimes a cell doesn't want to turn

有時細胞不想將所有的訊息

all of the messenger RNA it creates into protein,

都轉換成蛋白質

or it may need to destroy RNA injected into the cell

或者需要摧毀

病毒帶進來的 RNA

by an attacking virus.

Say, for example, in our cellular kitchen,

例如，在細胞廚房中

that someone wanted to cancel their order

有人想要取消點餐

or decided they wanted chips instead of fries.

或想用薯片取代薯條

That's where RNAi comes in.

這就是 RNAi 的用武之地

Thankfully, your cells have the perfect knives

所幸細胞有很好的刀具

for just this kind of job.

來執行這項工作

When the cell finds or produces

當細胞發現或產生

long, double-stranded RNA molecules,

長鏈雙股 RNA 分子

it chops these molecules up

它會用一種蛋白質砍下這些分子

with a protein actually named dicer.

就叫切丁酶！

Now, these short snippets of RNA

現在，這些 RNA 碎片

are floating around in the cell,

在細胞中漂蕩

and they're picked up by something called RISC,

之後被 RISC

the RNA Silencing Complex.

亦即 RNA 誘導沉默複合體撿起

It's composed of a few different proteins,

此類複合體由幾種蛋白質組成

the most important being slicer.

其中最重要的是切片酶

This is another aptly named protein,

這個蛋白質的名字非常貼切

and we'll get to why in just a second.

等一下便會明白了

RISC strips these small chunks

RISC 將雙股 RNA 之碎片

of double-stranded RNA in half,

一分為二

using the single strand to target matching mRNA,

接著將單股的碎片與 mRNA 接合

looking for pieces that fit together

找適合的配在一起

like two halves of a sandwich.

就像是三明治的兩半

When it finds the matching piece of mRNA,

配對成功後

RISC's slicer protein slices it up.

RISC 便將它切片

The cell then realizes

這時細胞就了解到

there are odd, strangely sized pieces

他們是奇怪的 RNA 碎片

of RNA floating around

四處飄浮

and destroys them,

並破壞它們

preventing the mRNA from being turned into protein.

藉此避免 mRNA 轉換成蛋白質

So, you have double-stranded RNA,

所以當出現雙股 RNA 時

you dice it up,

就會被切丁

it targets mRNA,

再和對應的 mRNA 結合

and then that gets sliced up, too.

結合後又再被切片

Voila!

厲害吧！

You've prevented expression

由此可防止基因表現

and saved yourself some unhappy diners.

並謝絕不開心的用餐客人

So, how did anybody ever figure this out?

但是，這是怎麼被發現的呢？

Well, the process was first discovered in petunias

這個嘛，這個過程 首先在牽牛花中發現

when botanists trying to create deep purple blooms

當時植物學家試圖培育深紫色的花朵

introduced a pigment-producing gene into the flowers.

將一種紫色色素基因打入花朵中

But instead of darker flowers,

但是除了有暗色系花朵

they found flowers with white patches

他們還發現有白斑的花

and no pigment at all.

或是完全沒有色素的花

Instead of using the RNA produced by the new gene

花朵沒有用新基因產生的 RNA

to create more pigment,

去創造更多色素

the flowers were actually using it

反而是用此 RNA

to knock down the pigment-producing pathway,

去擊倒色素產生路徑

destroying RNA

從植物原有的基因和 RNAi

from the plant's original genes with RNAi,

去催毀 RNA

and leaving them with pigment-free white flowers.

使植物剩下沒有色素的白色花朵

Scientists saw a similar phenomena

科學家在某種線蟲中

in tiny worms called C. elegans,

也找到類似的現象

and once they figured out what was happening,

一旦他們想通發生了什麼事

they realized they could use RNAi

他們就了解到可以用 RNAi

to their advantage.

去達到他們的目的

Want to see what happens

想要看看某個基因

when a certain gene is knocked out of a worm

被驅趕出一隻蚯蚓

or a fly?

或一隻蒼蠅會發生什麼事嗎？

Introduce an RNAi construct for that gene,

為那個基因打造一個專屬 RNAi

and bam!

就好啦！

No more protein expression.

再也沒有蛋白質（基因）表現

You can even get creative

你甚至可以發揮創意

and target that effect to certain systems,

針對某些系統發揮作用

knocking down genes in just the brain,

在腦袋中擊毀基因

or just the liver,

或在肝中

or just the heart.

或在心臟中

Figuring out what happens

搞清楚

when you knock down a gene in a certain system

在特定系統擊倒某個基因 會有什麼後果

can be an important step

是重要的一步

in figuring out what that gene does.

搞清楚這個基因到底在做什麼

But RNAi isn't just for understanding

但 RNAi 不只是為了瞭解

how things happen.

事情怎麼發生

It can also be a powerful, therapeutic tool

它還可以當療效性強大的工具

and could be a way for us to manipulate

而且可能是一個讓我們去操縱

what is happening within own cells.

在細胞中發生的事的方法

Researchers have been experimenting

研究人員已經試驗

with using it to their advantage in medicine,

在醫藥上利用他們的優點

including targeting RNA and tumor cells

包括找出 RNA 和癌細胞

in the hopes of turning off cancer-causing genes.

並期望把癌症基因去除

In theory, our cellular kitchens

理論上，我們的細胞廚房

could serve up an order of cells,

可以為細胞上菜

hold the cancer.

謝絕癌症點餐