Structural organization of nuclear complexes containing DNA-like RNA

In previous reports it was shown that the main part of nuclear DNA-like RNA (D-RNA) can be found in homogeneous 30 s particles which are complexes of specific protein particles with D-RNA strands bound to them. It has now been established that 30 s particles are monomers of a more complex polysome-like structure. Such a structure is formed by a long D-RNA strand and a number of globular protein particles bound to it and tightly packed along the D-RNA strand. These complexes occupy a wide zone in sucrose gradients between 30 and 200 s. In the electron microscope, one finds the 30 8 peak contains only single particles; the 45 s peak, dimers; the 55 to 60 s peak, trimers, and so on. In heavier zones long chains of particles ( n = 8 to 12) were observed. Treatment with small amounts of RNase quantitatively converts large polyparticles into the 30 s particles. The buoyant density and the protein composition of mono- and poly-particles are the same. They are very different from those of ribosomes. The sedimentation coefficient of RNA isolated from particles is related to the number of monomers in the complex. It is calculated that one protein particle is bound to an RNA strand having a molecular weight of about 2 × 10 5. The structure and function of the nuclear complexes containing D-RNA are discussed. The name “informofer” is suggested for monomeric protein particles.