Saturday, November 17, 2007

This Week's Citation Classic

Volkin E & Astrachan L. 1956. Phosphorus incorporation in Escherichia coli ribonucleic acid after infection with bacteriophage T2. Virology 2 (2): 149-161.

After the discovery of DNA structure by Watson and Crick, the way seemed paved to a quick resolution of how proteins were made. Unfortunately, both theory and experiment quickly stalled at an impasse. Data from several labs was extremely difficult to interpret, namely findings that 1) for several bacterial species, DNA bases varied widely, but the cytoplasmic RNA did not (Belozersky & Spirin 1958) and 2) the cytoplasmic RNA was exceptionally stable (Davern & Meselson 1960). These findings seemed to suggest it was impossible for RNA to be a template for protein synthesis.

The problem was that this cytoplasmic RNA was not what later came to be known as messenger RNA (mRNA), but rather a relatively "inert" form of RNA associated with ribosomes (i.e. rRNA)(Note: rRNA is now thought to carry out key reactions during translation).

On Good Friday 1960, Sidney Brenner, Francis Crick and Francois Jacob were hanging out at Brenner's rooms at King's College when they put together some anomalous data and created a theory to explain protein synthesis. These data were 1) Hershey et al.'s (1953) discovery of a small fraction of RNA that was synthesized rapidly just after phage infection, 2) Pardee et al.'s observation of extremely rapid enzyme synthesis following mating between two bacterial types and 3) a report from two relative unknowns, Eliot Volkin and Lazarus Astrachan, from Oak Ridge National Laboratory.

Volkin and Astrachan infected E. coli with phage, then exposed the culture to radioactive 32P for a few minutes. What they found was a "DNA-like RNA" that did not resemble the previously found RNAs (i.e. rRNA and tRNA) and turned over very rapidly. The main difference was that it had similar bases to the DNA of phage.

f DNA labelled f RNA E. coli DNA E. coli RNA
A 32 33 25 26
U or T 32 29 25 19
C 18 20 25 25
G 17 18 25 19

What Volkin and Astrachan did not realize is that they discovered the key to solving the protein synthesis mystery.

Crick describes the Good Friday Meeting in What Mad Pursuit, "What the PaJaMo [i.e. Pardee et al. 1959] type of experiment showed was that the ribosomal RNA could not be the message.... Where, then, is the message? At this point Sydney Brenner let out a loud yelp -- he had seen the answer. (So had I, for that matter, though nobody else had). One of the peripheral problems of this confused subject had been a minor species of RNA [found by Volkin and Astrachan] that occurred in E. coli ... [Volkin and Astrachan's] result had hung in midair, surprising but unexplained.... What Sydney had seen was that the Volkin-Astrachan RNA was the messenger RNA for the phage-infected cell... It is difficult to convey two things. One is the sudden flash of enlightenment when the idea was first glimpsed. It was so memorable that I can recall just where Sydney, Fran├žois, and I were sitting in the room when it happened. The other is the way it cleared away so many of our difficulties. Just a single wrong assumption (that the ribosomal RNA was the messenger RNA) had competely messed up our thinking, so that it appeared as if we were wandering in a dense fog."

Paul Berg, winner of the 1980 Nobel Prize in Chemistry, calls Volkin and Astrachan's research an "unsung but momentous discovery of a fundamental mechanism in genetic chemistry" and a "seminal discovery [that] has never received its proper due."

What happened? Everybody knew of Volkin and Astrachan's findings at the time. In an interview at his Oak Ridge home in late 2003, Volkin recalled his conversation with Sydney Brenner at Cold Spring Harbor Laboratory in New York, where Volkin conducted research on the hot topic of bacterial viruses during the summers in the late 1950s. "I can well remember sitting on the lawn at Cold Spring Harbor and telling Sydney Brenner about our experiments," Volkin says. "I gave a presentation on our RNA research to the group there." In a 1977 issue of Nature, renowned biophysicist T. H. Jukes wrote that in 1956, "I had squeezed my way into a doorway of a packed room to hear a paper by Volkin and Astrachan on DNA-like RNA." (ORNL).

The problem was that Volkin and Astrachan's data was self-admittedly "sloppy", Volkin and Astrachan weren't well known, ORNL wasn't highly regarded and the data simply did not fit with the dominant paradigm at the time. Brenner, Crick and Jacob ended up getting recognized with "discovering" mRNA, while Volkin and Astrachan were never properly credited. Many scientists felt Volkin and Astrachan deserved Nobel recognition.

Belozersky AN & Spirin AS. 1958. A correlation between the compositions of the deoxyribonucleic and ribonucleic acids. Nature 182: 11–112.

Hershey AD, Dixon J & Chase M. 1953.Nucleic acid economy in bacteria infected with bacteriophage T2 .1. Purine and pyrimidine composition. Journal of General Physiology 36 (6): 777-789.

Davern CI & Meselson M. 1960. Molecular conservation of ribonucleic acid during bacterial growth. Journal of Molecular Biology 2: 153.

Pardee AB, Jacob F & Monod J. 1959. Genetic control and cytoplasmic expression of inducibility in the synthesis of Beta-galactosidase by E. coli. Journal of Molecular Biology 1 (2): 165-178.

Photo: One of the early RNA electron micrographs scanned with the vidicon/RTPP system (Jacob Maizel, Bruce Shapiro, and Lewis Lipkin). The sample was adenovirus type 2 messenger RNA. Bruce developed boundary segmenters and boundary shape descriptors that could map electron micrograph data to the secondary structure.


  1. May I recount a story that is related to the discovery of mRNA? It must have been early in 1961 when Salvador Luria came to give a seminar at the University of Florida, where I was a young faculty member. The event was so momentous that we went as a delegation to pick him up at the small Gainesville airport. (An aside: When he got off the plane, he looked around and exclaimed "I hate palm trees!")

    The remarkable thing is that when he got up to talk to the assembled throng, he declared that he wouldn't present his own research because he had just received a preprint of work that he considered far more important. What he talked about was the paper by Brenner, Crick and Jacob annuncing the discovery of mRNA!

  2. Nice post!

    Nice blog, too (came here via Sandwalk). However, may I humbly suggest you consider a different color scheme? I don't want to offend, but the white text on black background makes everything seem to swim as I'm reading it.