You'd Prefer An Argonaute

Why was the the Argonaute (Ago) protein named “Argonaute?” Why wasn’t it named “The Slicenator”, or “Chopinator” or some other cool sounding name reflecting the activity many Ago proteins possess? Or, following Eric Lander‘s description of Ago’s activity as “enzymatic kung-fu” (beginning at 7:20 in Part 1) in the wonderfully done NOVA program introducing RNAi below, how about “sensei”?

Part 1 of the NOVA RNAi program:

Part 2 of the NOVA RNAi program:

The answer to the above question is that the cleavage activity of plant AGO1 of nearly perfect matched targets was not completely worked out at the time it was named. What follows below is a simple graphic depicting the most well characterized domains of Argonaute, a very brief history of how the protein was named, and where the name comes from.

The above graphic is from a class presentation I gave in 2007. Not shown/labeled are the N-terminal or Mid domains also common to eukaryotic Argonaute proteins.

Arabodopsis AGO1 mutant, 1998 (1)

Drawing of Argonauta Argo, male and female, 18th century (2)

The name Argonaute comes from phenotypes observed for AGO1 mutants in Arabidopsis thaliana by Bohmert and collaborators in 1998 (1). To the researchers eyes, the plants resembled the tentacles of the pelagic octopus, Argonauta argo. In the paper, the authors state:

Because of their unusual appearance, which reminded us of a small squid, we named these mutants argonaute.

So then how were the marine Argonauts named? It is thought that early taxonomists were enamored with tales of sitings of Argonauts “sailing” along the surface of the sea; females using their paper-thin eggcase shell as a boat, and their webbed dorsal arms (in the drawing above the webbed portions are resting against side of shell) raised above the surface acting as sails (6). (This method of propulsion is today considered a myth, as it has never been observed by marine scientists.) To these taxonomists perhaps this image bore semblance to great ancient wooden sail ships, like “Argo”, (built by Argus, who may have come from the city of Argos), sailed by Jason and the Argonauts in Greek mythology. The Argonauts –named for the ship they sailed– were a group of brawny, fearless men selected by Jason to join him on his perilous journey to recover the “Golden Fleece”, an undertaking that would finally allow him to rightfully claim the throne as king of Iolcus.

In 1963, a movie was released depicting this mythical tale. The movie is pretty good, and apparently was a special effects pioneer in its day. An unofficial trailer:

The word Argonaute has been used in a variety of other contexts as well. For example, in the 1950’s the French navy named their flagship submarine “Argonaute.” The “Argonaut Conference” was the codename for the Yalta Conference held in Crimea in 1945 that brought together Winston Churchill, FDR, and Joseph Stalin.

In attendance at the Argonaut Conference, 1945: Winston Churchill, FDR, and Joseph Stalin (3)

Argonaute phylogenetic tree, present day (5). Argonaute-like group in black, PIWI-like group in green, C. elegans group 3 in red

A sharp increase in genome sequencing and small RNA research in the last decade has lead to the discovery of many more Argonaute genes (including Ago, PIWI-like, and Group 3 in worms (4)), a trend that will surely continue.

Presently in C. elegans, there are >25 known Argonaute genes; 10 in plants; 8 in humans (4 Agos and 4 PIWIs) (5).

Feeling a bit depleted of Argonautes myself, I reckon I’d prefer a few more.

References:

1. Bohmert et al., The EMBO Journal Vol.17 No.1 pp.170–180, 1998.
2. Internet (reference forthcoming)
3. http://en.wikipedia.org/wiki/Yalta_Conference
4. Analysis of the C. elegans Argonaute family reveals that distinct Argonautes act sequentially during RNAi.; Cell. 2006
5. Hutvagner and Simard, Nature Reviews Molecular Cell Biology 9, 22-32, January 2008.
6. http://researchdata.museum.vic.gov.au/argosearch/index.html