(1973); T. Seebeck and R. Weil, ibid. 13, 567 (1974); R. T. Su and M. L. Depamphilis, Proc. Natl. Acad. Sci. U.S.A. 73, 3466 (1976). 26. R. J. Shmookler, J. Buss, M. H. Green, Virology 57, 122 (1974); M. H. Green and T. L. Brooks, ibid. 72, 110 (1976). 27. J. McMillen and R. A. Consigli, J. Virol. 14, 1326 (1974); W. Meinke, M. R. Hall, D. A. Goldstein, ibid. 15, 439 (1975). 28. A. J. Varshavsky, V. V. Bakayev, P. M. Chumackov, G. P. Georgiev, Nucleic Acids Res. 3, 2101 (1976). 29. J. D. Griffith, Science 187, 1202 (1975). 30. J. E. Germond, B. Hirt, P. Oudet, M. GrossBellard, P. Chambon, Proc. Natl. Acad. Sci. U.S.A. 72, 1843 (1975). 31. C. Cremisi, P. F. Pignatti, 0. Croissant, M. Yaniv, J. Virol. 17, 204 (1976). 32. H. Zentgraf, W. Keller, U. Miller, Philos. Trans. R. Soc. London Ser. B 283, 299 (1978). 33. W. Bauer and J. Vinograd, in Basic Principles in Nucleic Acid Chemistry, P. 0. P. T'so, Ed. (Academic Press, New York, 1974), vol. 2, pp. 262305. 34. G. Christiansen and J. D. Griffith, Nucleic Acids Res. 4, 1837 (1977); J. D. Griffith and G. Christiansen, Cold Spring Harbor Symp. Quant. Biol., in press; A. J. Varshavsky, S. A. Nedospasov, V. V. Schmatchenko, V. V. Bakayev, P. M. Chumackov, G. P. Georgiev, Nucleic Acids Res. 4, 3303 (1977). 35. F. B. Fuller, Proc. Nail. Acad. Sci. U.S.A. 68, 815 (1971). 36. F. H. C. Crick, ibid. 73, 2639 (1976). 37. J. C. Wang, J. Mol. Biol. 55, 523 (1971); J. J. Champoux and R. Dulbecco, Proc. Natl. Acad. Sci. U.S.A. 69, 143 (1972); W. Keller, ibid. 72, 2550 (1975); H.-P. Vosberg and J. Vinograd, Biochem. Biophys. Res. Commun. 68, 456 (1976). 38. D. Nathans and K. J. Danna, J. Mol. Biol. 64, 515 (1972). 39. R. Hancock, ibid. 86, 649 (1974). 40. M. L. Depamphilis, P. Beard, P. Berg, J. Biol. Chem. 250, 4340 (1975). 41. W. Keller, Proc. Natl. Acad. Sci. U.S.A. 72, 4876 (1975). 42. H. H. Ohlenbusch, B. M. Olivera, D. Tuan, N. Davidson, J. Mol. Biol. 25, 299 (1967). 43. In the electron microscope, the material from this region of the sucrose gradient (Fig. 4b, fraction 14) showed small capsidlike structures of irregular, often filamentous shapes. The absence of these structures from sucrose gradient fractions containing 0.6AM sodium chloride (Fig. 4) indicate that they may represent salt-unstable capsomeric aggregates [C. F. T. Mattem, K. K. Takemoto, A. M. DeLava, Virology 32, 378 (1967)]. 44. M. Bellard, P. Oudet, J.-F. Germond, P. Chambon, Eur. J. Biochem. 70, 543 (1976). 45. M. Renz and L. Day, Biochemistry 15, 3220 (1976). 46. M. Shure and J. Vinograd, Cell 8, 215 (1976). 47. R. E. Depew and J. C. Wang, Proc. Natl. Acad. Sci. U.S.A. 72, 4275 (1975); D. E. Pulleyblank, M. Shure, D. Tang, J. Vinograd, H.-P. Vosberg, ibid. 72, 4280 (1975). 48. F. H. C. Crick and A. Klug, Nature (London) 255, 530 (1975); H. M. Sobell, C.-C. Tsai, S. G. Gilbert, S. C. Jain, T. D. Sakore; Proc. Natl. Acad. Sci. U.S.A. 73, 3068 (1976); J. F. Pardon, D. L. Worcester, J. C. Wooley, R. I. Cotter, D. M. Lilley, B. M. Richards, Nucleic Acids Res. 4, 3199(1977). 49. M. Levitt, Proc. Natl. Acad. Sci. U.S.A. 75,640 (1978). 50. J. Sambrook, P. A. Sharp, W. Keller, J. Mol. Biol. 70, 57 (1972). 51. M. Botchan, E. Lacy, T. Maniatis, W. Keller, unpublished data. 52. H. Weintraub, A. Worcel, B. Alberts, Cell 9, 409 (1976). 53. R. W. Davis, M. Simon, N. Davidson, Meth. Enzymol. 21, 413 (1971). 54. J. 0. Thomas and R. D. Kornberg, Proc. Natl. Acad. Sci. U.S.A. 72, 2626 (1975). 55. W. Keller and I. Wendel, Cold Spring Harbor Symp. Quant. Biol. 39, 199 (1974). 56. D. R. van der Westhuyzen, E. L. Bohm, C. van Holt, Biochim. Biophys. Acta 359, 341 (1974). The histones were extracted from the nuclei of HeLa cells. 57. We thank Drs. Francis Crick, Ada Olins, Donald Olins, Manfred Renz, and Joe Sambrook for suggestions, comments, and criticism and Drs. Gunna Christiansen and Jack Griffith for sending us a manuscript of their paper. An account of some of the results of this investigation has been given at the 1977 Cold Spring Harbor Symposium on chromatin. This work was supported by a grant (Ke 134/3) from the Deutsche Forschunggemeinschaft and by the Stiftung Volkswagenwerk.