472 ROLLIN D. HOTCHKISS 



The cytoplasmic factor, kappa, of Paramecium aurelia which brings about 

 production of "killer" substance, has been shown in Sonneborn's laboratory 

 to give some of the specific reactions of the DNA-proteins.^" Since kappa 

 behaves like a self-determining invading particle, although influenced by 

 the host genes, its DNA may be supposed to serve the same presumably 

 genetic type of function as does that of the viruses or Rickettsiae. More 

 remarkable, perhaps, is the fact that the "infected" paramecia liberate into 

 their culture fluid a DNA-protein, paramecin, which is the actual sub- 

 stance^^^ killing the sensitive animals. The finding that this DNA-protein 

 can bring about the death of those organisms which are not bearing kappa 

 particles, and therefore already producing it, does not at the moment fit 

 simply into the genetic chemical picture of DNA function. 



Small DNA-containing bodies have been reported in the cytoplasm of 

 pollen mother cells of several plant species j^^^ these bodies are believed to 

 be associated with, or derived from, the nucleus. Somewhat similar bodies 

 are described in the nucleolus-associated chromatin of nerve cells ;^"^ these 

 may or may not bear a relation to the chromosomes. Leuchtenberger and 

 Schrader^^" have reported that photometrically determined nuclear DNA 

 varied over a range of 30:1 in salivary gland cells of Helix, and character- 

 istically and progressively decreased as the secretion product (cytoplasmic 

 polysaccharide) was produced. This would seem to imply a rather direct 

 participation of nuclear DNA in cellular function. 



A temporarily elevated DNA content of plant tissues inoculated with 

 virulent crown-gall bacteria is said to parallel the presence of tumor-induc- 

 ing principle, one of the factors leading to subsequent formation of a 

 crown-gall tumor .^^^ These findings are taken to suggest the possible identity 

 of the tumor principle with the new DNA formed in the infected host at 

 that time. As mentioned above, the same workers had reported the transfer 

 of virulence from strain to strain in the bacteria themselves through DNA- 

 containing preparations made from virulent strains. 



Preparations of /3-glucuronidase from calf spleen, inactivated by dilution, 

 are restored to full activity by DNA preparations.^^- Since depolymerized 

 DNA and, to some extent, PNA are also effective, the possibility that 

 DNA is some sort of coenzyme seems more remote than that it contributes 

 another activator, possibly specific metal ions, to the enzyme system. 



"7 J. R. Freer, Am. Naturalist 82, 35 (IMS) ; Genetics 33, 625 (1948). 



228 W. J. van Wagtendonk, /. Biol. Chem. 173, 691 (1948). 



229 A. H. Sparrow and M. R. Hammond, Am. J. Botany 34, 439 (1947). 



230 C. Leuchtenberger and F. Schrader, Proc. Natl. Acad. Sci. U. S. 38, 99 (1952). 



231 R. M. Klein, Am. J. Botany 40, 597 (1953). 



232 P. Bernfeld and W. H. Fishman, J. Biol. Chem. 202, 757 (1953). 



