RNAi: The Dream Makes a Comeback

This Promega Notes Cover from 2004 celebrated the potential stop and go power of DNA-directed RNAi.
This Promega Notes Cover from 2004 celebrated the potential stop and go power of DNA-directed RNAi.

In the early 2000s, RNAi was a hot topic. The science world was abuzz with all the possibilities that harnessing this natural process could hold. And why not? The idea of posttranscriptionally silencing genes using only a small fragment of double-stranded RNA is huge—big enough to earn the scientists who discovered it a Nobel Prize in 2006.

The process of RNAi starts with short (~70 nucleotieds), double-stranded fragments of RNA called short hairpin RNAs (shRNA). These shRNAs are exported into the cytoplasm and cleaved by the enzyme Dicer into smaller pieces of RNA that are about 21 nucleotides long and are referred to as small interfering RNAs (siRNA). The siRNAs reduce or stop expression of proteins through a sequence of events where the antisense strand of the siRNA is incorporated into and RNA-induced silencing complex (RISC), which then attaches to and degrades its complimentary messenger RNA, thereby reducing or completely stopping expression.

It turned out, however, that harnessing the promise of RNAi was a little trickier than anticipated. Continue reading “RNAi: The Dream Makes a Comeback”

Promising Treatment for Marburg Virus Hemorrhagic Fever

This negative stained transmission electron micrograph depicts a number of filamentous Marburg virions. Note the virus’s characteristic “Shepherd’s Crook” shape; Magnified approximately 100,000x. Content Providers(s): CDC/ Dr. Erskine Palmer, Russell Regnery, Ph.D., via Wikimedia Commons
I admit to some trepidation about the diseases that may be harbored in my backyard. For example, do the mice in my yard and, despite my and my cats’ efforts, in my house carry deer ticks that harbor the bacterium Borrelia burgdorferi, which causes Lyme disease? Should I be keeping an eye on the vitality of the birds around my property and density of my local mosquito population for potential risk of West Nile Virus transmission? As troublesome as these infections can be, mortality is low for infected humans. Contrast that with the mortality rate of up to 90% for the filoviruses Ebola and Marburg. I find it easy to dismiss these viruses because the reservoir (asymptomatic host) is not in the Upper Midwest but rather Africa, but the tragedy of the Ebola outbreak in the West African countries of Liberia, Sierra Leone and Guinea demonstrates the number of lives lost in an epidemic. Currently, there is no therapy or vaccine to treat these deadly viruses other than transferring antibodies from survivors to those infected. Therefore, the article in Science Translational Medicine about an antiviral treatment that protected macaques injected with a lethal dose of Marburg virus was welcome news. Continue reading “Promising Treatment for Marburg Virus Hemorrhagic Fever”