Re: Cancer's Sinister Helpers

September 9, 2010

My cousin, a molecular biologist, comments:

Micro RNAs are yet another revolution in cell, molecular, and

developmental biology. I first became aware of them about ten years ago

when they were being engineered as tools to disrupt gene expression in

model systems such as C. elegans. As is so often the case, the ability

of these so called silencing RNAs (siRNAs) to knock down gene expression

in C. elegans was at first considered to be just a curiosity. Over the

last decade or so, however, their profound importance in regulating gene

expression in many model organisms (including mouse) has been

appreciated. Thus far, the role they play in the development of

metazoans has been best characterized, but I'm sure they will be

implicated in many other phenomena in years to come (e.g., the cancer

article).

The importance of micro RNAs is perhaps best understood by putting them

in the larger context of the expanding role for RNA in general. As I'm

sure you know, RNA has now been demonstrated to perform catalytic

functions in many processes, and of course, the self- splicing activity

of some RNAs has led to the idea that RNA was the first nucleic acid on

earth. Back when you first learned about ribosomes, the ribosomal

proteins were assumed to do the catalytic work while the ribosomal RNAs

were thought to serve only a structural role. Now the thinking has

reversed: Ribosomal RNAs are thought to play important catalytic roles

during translation while most ribosomal proteins are merely scaffolding.

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Randy posted:

Cancer's Sinister Helpers

When tiny hairpin-shaped molecules act up, they don't rebel loner-style

like Dean. Instead they take on the persona of Darth Vader,

crushing proteins under their command and turning acquaintances to the

dark side as well. In this case, though, the fight is for control not of

the universe, but of the body. And a dark-side victory could end in

cancer.

No one would have predicted a decade ago that these microRNAs, as the

hairpins are called, were involved in cancer, because no one even knew

that

they existed in people. Mere snippets of RNA -- DNA's underappreciated

cousin -- these micromolecules are about 22 chemical letters long. But

their size

belies their power.

When on their best behavior, the molecules are competent and capable

managers of the protein-building process that keeps a cell humming in

perfect

harmony. But when microRNAs go rogue, the results can be disastrous.

September 9, 2010