198 ( IIAPTF.R 40 



vitro, whereas nonacetylated histones sup- matin contains a smaller percentage of 



press RNA synthesis. That histone acetyla- acetylated histone than dispersed (function- 



tion may be a mechanism for controlling ing) chromatin. 



cene action in vivo is supported by the find- .- D .,,-,,, v/ ,• A m<v„. i u c— »., 



KK - ''By V. C . Littau, V. U. Allfrey. J. H. Frenster. 



ing 1T that clumped (nonfunctioning) chro- and A. E. Mirsky (1964). 



SUMMARY AND CONCtUSIONS 



Puffs in dipteran polynemic chromosomes and loops of lamphrush chromosomes in 

 amphibian oocytes are unwound, genetically active regions. 



From the standpoint of behavior, two kinds of DNA occur. One type is conserved 

 as a regular part of the chromosome and is genetic material; the other type is not con- 

 served — although nucleus-derived — and may be found in the cytoplasm or in the 

 nucleus. No clear evidence exists that nonconserved DNA has genetic properties. 



Basic proteins form complexes with DNA. These complexes are either deoxyribo- 

 nucleohistones or deoxyribonucleoprotamines. Noncomplexed DNA and nucleopro- 

 tamines support the synthesis of DNA-dependent RNA. On the other hand, different 

 histones have different capacities to inhibit DNA synthesis and DNA-dependent RNA 

 synthesis when complexed with DNA as nucleohistones. Nonfunctioning chromatin 

 contains a smaller percentage of acetylated histone than functioning chromatin. In- 

 hibition of gene action by histones may be accomplished by increasing the denatura- 

 tion temperature of DNA; by causing chromosome coiling; or by other, presently- 

 unknown means. In any event, it is likely that in higher organisms, the use of DNA 

 as a template is regulated to a large extent by histones. 



REFERENCES 



Allfrey, V. G., Faulkner, R., and Mirsky, A. E., "Acetylation and Methylation of His- 

 tones and Their Possible Role in the Regulation of RNA Synthesis," Proc. Nat. 

 Acad. Sci., U.S., 51:786-794, 1964. 



Allfrey, V. G., Littau. V. C, and Mirsky, A. E., "On the Role of Histones in Regulating 

 Ribonucleic Acid Synthesis in the Cell Nucleus," Proc. Nat. Acad. Sci., U.S., 49: 

 414-421. 1963. 



Allfrey, V. G., and Mirsky, A. E., "Evidence for the Complete DNA-Dependence of 

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 1596. 1962. 



Becker. H. J.. "Die genetischen Grundlagen der Zelldifferenzierung," Naturwissenschaf- 

 ten. 5! :205 -211, 230-235, 1964. 



Beermann, W.. Reisenchromosomen, Protoplasmologia, 6:1-160, 1962. 



Beermann, W., and Clever. U., "Chromosome Puffs," Scient. Amer.. 210 (April): 

 50-58, 156, L964. 



Beermann. W., Hess, O.. and Meyer. G. F.. "Structure and Function of the Y Hetero- 

 chromatin in Drosophila," Proc. XVI Int. Congr. Zool., 4:283-288. 1963. 



