You have to spend money to make money

(Introductory comment – this is a verbatim repost of an essay originally published on The Panda’s Thumb.)

In biology, genetics, biochemistry, and molecular biology classes, one of the things that we used to learn that distinguishes prokaryotes from eukaryotes is the “fact” that eukaryotes have polyadenylated mRNAs, while prokaryotes do not. This morphed rather easily into a distinction – eukaryotes do polyadenylation, prokaryotes do not. For years, this was standard fare in class. However, even as generations of students (beginning with the discovery of polyadenylate tracts in hnRNA in eukaryotes) were learning of this distinction, we knew that all was not right with this. Among the lurking pieces of conflicting data was that the first biochemical entity that was shown to add poly(A) tracts to RNAs in vitro was a bacterial one, isolated and purified from E. coli (1).

Polyadenylation – the process

Previously, I summarized the importance of the poly(A) tail of mRNAs. As I stated in that essay (and as one can tell by perusing the background stuff and some of the links here), what I am interested in is how the poly(A) tail is actually added to a mRNA. The point of this essay is to provide an overview of what we know, so that future essays on the subject may have a better context. I’ll structure this essay as a series of bullets (ideally, they’d be concise, but knowing me that’s not too likely).