Theory of inactivation and reactivation of transforming DNA

Abstract

synopsisA simple quantitative theory of inactivation of transforming DNA has been formulated. It is based on the idea that genetic recombination of the molecule of transforming DNA with the bacterial genome is possible only from the point mutation of the gene up to the nearest hit or point of damage on the corresponding DNA molecule. Our data and the data of other authors on the kinetics of inactivation by HNOz or U.V. light or both are consistent with these theoretical predictions. Theoretical predictions were made concerning the extent of reactivation by fusion and annealing of damaged DNA with a diluting genetically inactive DNA. These estimates have been reasonably confirmed by our experimental results.

Biosynthesis of Riboflavin, Folic Acid, Thiamine, and Pantothenic Acid

“…However, convincing evidence for regulation of the pathway by coordinate repression in B. subtilis has been reported by Bacher and coworkers (31,33,34) and by the extensive investigations of Bresler and his collaborators reported in a series of papers on the "riboflavin operon" (8,10,24,28,32,(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48). The latter workers have mapped the regulatory and structural genes involved and their work has also been of great significance in the elucidation of individual steps of the biosynthetic pathway (discussed earlier).…”

“…This has been established by studies on the incorporation of I4C-labeled species of guanosine into riboflavin in S. typhimurium (9, P. guillieimondii (13,14) E. ashbyii (7,15), and B. subtilis (8) and decisively confirmed with the discoveries of enzymes from various sources that catalyze the reduction of the nucleotidyl ribose group (13,16,17). The earlier contention that ribitol and ribose are preferentially incorporated into the ribityl group of riboflavin (1 [8][9][10][11][12][13][14][15][16][17][18][19][20] was based on studies with whole cells under conditions in which the effects of pool sizes were hard to interpret and thus the conclusions were suspect. In fact, Miersch, one of the advocates of a precursor role for ribitol (18,19), has recently stated that earlier observations were inconclusive (1 3,2 1) and, with collaborators, has done some of the recent work to indicate that the ribityl group is derived from the ribose of GTP (1 3,2 1).…”

Enzymatic RNA synthesis on irradiated DNA

“…There will be a reduction of this length if a criticallesion is produced by irradiation within this interval of the DNA strand. According to the theory of BRESLER et al 21 concerning the recombination length of DNA for transformation, the interval L z between the binding site and the critical lesion bllows the equation:…”

“…where z is the average number of criticallesions on the two DNA strands within the length L o ' The derivation of equation (1) is given in detail by Bresler, Kalinin and Peromov (1964), who have used it to calculate the reduction in recombination length of a transforming DNA molecule with a bacterial chromasome. Since the amount of RNA synthesized is proportional to the length of the DNA interval transcribed, LzfL o represents the relative priming activity AzfA o as a function of z:…”

Nitrite Promotes Lymphoma Incidence in Rats

“…This interpretation of the sequence of events is speculative, but if it is correct, nitrite may not be acting as a "classical" direct carcinogen but rather as an indirect carcinogen or promoter. On the other hand, nitrite, like many know direct carcinogens, is mutagenically active (14)(15)(16)(17)(18)(19).…”