Section 3 — Molecular and Microbial Genetics 



are not incorporated a priori into the primary 

 structure of s-RNA but are acquired by the 

 methylation of the polynucleotide chain by a 

 multiple enzyme system - RNA methylase— 

 which uses s-adenosyl methionine as the methyl 

 donor.d) 



Studies of the RNA methylases from different 

 species revealed that the enzyme systems are 

 endowed with great species specificity. 



The s-RNA from a given source while fully 

 methylated with respect to its homologous 

 methylating enzymes can accept excess methyl 

 groups from an enzyme from a different species. 

 These findings tend to eliminate the possibility 

 that the methylated bases are involved in the 

 coding of amino acids. If it is assumed that the 

 amino acid code is universal, the methylating 

 enzymes of all species would be expected to be 

 uniform. Yet we found that a presumably fully 

 encoded s-RNA of one specieo can accept methyl 

 groups from a heterologous enzyme system. 



The species variation of the RNA methylases 

 has also been adumbrated by the analytical data 

 on the distribution of the methylated bases of 

 s-RNA from various sources. 



However, the biological function of the spe- 

 cies variation of the enzyme and, indeed, of the 

 methylation itself awaits elucidation. 



1. E. Fleissner and E. Borek, Proc. Nat. Acad. 

 ofSci., U.S.A. 48, 1199, 1962. 



3.5. Synthesis of Specific RNA on Different Sites of 

 the Phage T2 Chromosome in vivo and in 

 vitro. R. B. Kcesin, M. F. Shemjakin, G. M. 

 Gorlenko, I. A. Bass and A. A. Prozorow 

 (U.S.S.R.). 



1. Different types of phage-specific mRNAs 

 are synthesized during early and later stages of 

 the intracellular development of the phage T2 in 

 E. coli B. The phenomenon is in accordance 

 with the synthesis of different proteins during 

 those stages (early enzymes and phage particle 

 protein). Experiments on the formation of 

 complexes of C l4 -mRNA and phage DNA show 

 that the mRNAs, synthesized on different stages, 

 correspond to different regions of phage DNA. 



2. Experiments with chloramphenicol indicate 

 lhat the regulation of the synthesis of different 

 specific mRNAs depends on the synthesis of 

 proteins. 



3. In vitro experiments showed that phage 

 DNA, added as a primer to an extract from 

 uninfected E. coli cells, directed only the synthesis 

 of a type of mRNA, which is similar to that 



synthesized in vivo during the early stages of 

 infection. The same mRNA was obtained when 

 native deoxyribonucleoprotein from T2 phage, 

 DNA from phage-infected cells or renatured 

 T2-DNA were used as primer. 



4. Also in systems containing T2-DNA as a 

 primer and partially purified enzymes from un- 

 infected E. coli B or B. prodigiosan} cells only 

 early mRNA was synthesized. In the in vivo 

 experiments with RNA-polymerase it was pos- 

 sible to obtain the synthesis of specific mRNAs 

 formed on different regions of the phage chro- 

 mosome (DNA) in the infected cells. The isola- 

 tion and purification of DNA does not change 

 the order of reading of the genetic information. 



3.6. The Active Complex in Protein Synthesis. R. 



Haselkorn, V. Fried, and J. Dahlberg 

 (Chicago, U.S.A.). 



RNA from turnip yellow mosaic virus has 

 been used to characterize the complex responsible 

 for protein synthesis in cell-free extracts from 

 Escherichia coli. Three types of experiment 

 were performed, all utilizing zone centrifugation 

 through sucrose gradients. In the first type, 

 viral RNA and coli ribosomes are mixed, frac- 

 tionated on the gradient, and the RNA located. 

 Secondly, the RNA ribosome mixture is frac- 

 tionated, and the individual fractions are as- 

 sayed for their ability to incorporate amino 

 acids. Finally, the RNA-ribosome mixture is 

 allowed to incorporate amino acids, then frac- 

 tionated, and both the RNA and newly made 

 protein located. All three experiments give es- 

 sentially the same result, namely, that in the 

 cell-free system 5-10 per cent of the ribosomes 

 participate in protein synthesis and the active 

 complex consists of one 70S ribosome and one 

 molecule of viral RNA. 



3.7. A Model System for Studying the Genetic Deter- 

 minants of Protein Configuration. Charles J. 

 Epstein and Robert F. Goldberger (Bethes- 

 da, U.S.A.). 



It is generally accepted that the genetic infor- 

 mation contained in linear DNA molecules is 

 transferred, via messenger RNA, to linear 

 polypeptide chains. However, the process by 

 which these chains are converted to "native" 

 proteins is poorly understood. The reduction and 

 reoxidation of ribonuclease by Anfinsen, White 

 and co-workers provided a model system for 

 studying this process, and led to the conclusion 



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