a word from Dr. Colin Leakey

December 12th 2000 marks the 25th anniversary of the award of 1975 Nobel Prizes of Renato Dulbecco, Howard Temin and David Baltimore. Although they did not coin the name themselves their Nobel Prizes were for the discovery of reverse transcriptases i.e. RNA-dependent DNA polymerases produced by those RNA viruses now known as retroviruses. (Temin & Mizutani 1970, Baltimore 1970). This discovery was based on unravelling problems posed by much earlier work by Peyton Rous (1911) concerning the mode of replication of his eponymous sarcoma virus of chickens. The acknowledgement of reverse transcription, implicit in the Nobel award, destroyed the tidy paradigm incorporating James Watson’s and Francis Crick’s more celebrated Nobel of 1962, of a one way flow of information from DNA to RNA to Protein.

Howard Temin (1970, 1980) suggested that RNA-retroviruses evolved from cellular moveable genetic elements of eukaryotes. David Baltimore (1985) pointed out that reverse transcription allows evolution of the genomes of higher organisms by horizontal gene transfer. Their work led to the whole basis of genetic engineering; to aspects of genetic anthropology almost entirely overlooked by the evolutionary ‘Establishment’ until quite recently; and to a basis for horizontal two way flows of information between hosts and parasites, including pathogens. Finally retroviruses got a bad press from HIV and nobody, it seems, really wanted to know how common they might be and how much of our genomes may include alien cDNA from inheritance or infection (transfection) that usually remains ‘silent’. Meanwhile disarmed retroviruses in the form of retrovirus packaging cell lines were developed to produce synthetic defective retroviruses that might be used in intended genetic transfer (Mann, Mulligan & Baltimore, 1983), but there was a problem here in avoiding accidentally producing replication competent or neo-viruses (Miller & Buttimore, 1986).

TEMIN H.M. & MIZUTANI S. (1970)	RNA-directed DNA polymerase in virions of Rous sarcoma virus.	Nature 226 1211-1213
TEMIN H.H. (1970)		Persp. Biol. Med. 14 11-26
TEMIN H. (1980)	Origin of retroviruses from cellular moveable genetic Elements.	Cell 21 599-600
BALTIMORE D. (1970)	RNA-dependent DNA polymerase in virions of RNA tumor viruses.	Nature 226 1209-1211
BALTIMORE D. (1985)	Retroviruses and retrotransposons: The role of reverse transcription in shaping the eukaryotic genome.	Cell 40 481-482
MANN R, MULLIGAN R.C. & BALTIMORE D. (1983)	Construction of a retrovirus packaging mutant and its use to produce helper-free defective retroviruses.	Cell 33 153-159
ROUS P (1911)	A sarcoma of the fowl transmissible by an agent separable from the tumor cells.	J. Exp.Med. 13 397-411
MILLER A.D. & BUTTIMORE C. (1986)	Redesign of retrovirus packaging cell lines to avoid recombination leading to helper virus production.	Mol. Cell. Biol. 6 2895-2902