VI. RNA AND CODING PROBLEMS 279 



minutes, though the cells are capable of producing a full complement 

 of phage if again given adenine. It seems feasible, then, to interpret these 

 results to mean that a certain degree of stoichiometry exists between 

 the messenger RNA and its specific product and that, as a result of its 

 action in relaying the message, the RNA is concomitantly inactivated. 

 Since T2 production ceases so abruptly, it must be assumed that the 

 protein product (s) involved are not limited to the T2-induced enzymes 

 but include phage protein itself. 



IV. Attempts at Isolation of a Messenger RNA 



Some purification of highly radioactive RNA (presumably enriched 

 in messenger RNA) from pulse-type experiments has been attained from 

 both T2-infected and nomially growing E. coli by classical centrifuga- 

 tion techniques (Volkin and Astrachan, 1956b, 1957) and by centrifuga- 

 tion through sucrose gradients (Nomura et al., 1960). Since the over-all 

 nucleotide compositions of these partially purified fractions were not 

 unlike total RNA, it was evident that only a small degree of purification 

 was made. In view of the observed heterogeneity of messenger RNA as 

 it exists in the cell (Hayashi and Spiegelman, 1961), the inadequate 

 results of such fractionations by centrifugation are not surprising. Spe- 

 cific hybrid formation of homologous DNA with messenger RNA as 

 effected by Hall and Spiegelman (1961) obviously should represent a 

 purified RNA product. On one such occasion this was proved for the 

 T2-specific RNA banded with T2 DNA in the cesium chloride gradient 

 (B. D. Hall and L. Astrachan, unpublished experiments). This method, 

 by limitations in its scale, is not readily applicable to the mass isolation 

 of messenger RNA. An ingenious technique has now been described 

 which has been used to isolate highly purified messenger RNA and 

 which lends itself to use on a preparative level. Bautz and Hall (1962), 

 employing a column of denatured T4 DNA coupled to acetylated, 

 phosphorylated cellulose, obtained specific interaction of it with only 

 messenger RNA, the bulk of the RNA from the T4-infected cell passing 

 through the column. The specific RNA, adsorbed to the DNA at a 

 temperature favorable for annealing with DNA, was recovered by 

 heating at elevated temperatures and elution. That the method is in- 

 herently specific is evident from the remarkable observation that mes- 

 senger RNA specific for DNA of a T4r7/ mutant has thus been purified. 



Isolation by ECTEOLA column chromatography of DNA-RNA com- 

 plexes has been accomplished from N'eurospora extracts by Schulman 

 and Bonner (1962) and from ovarian frog egg preparations by Finamore 

 and Volkin (1961). This technique may serve as a basis for the mass 

 isolation of such complexes or of the specific RNA itself. 



