Particles containing small molecular weight nuclear RNAs (snRNPs). Structure and possible functions

Abstract

Recent knowledge on snRNPs is reviewed in this paper. The relevant findings of our laboratory were essentially as follows: Particles containing small nuclear RNAs (snRNAs) were characterized ten years ago. More recently Lerner et al. have shown that particles containing snRNAs react with antibody produced in autoimmune disease. Furthermore, the snRNA (some of them are probably involved in 'splicing') were found associated with hnRNP. In the present work we have studied structures, extracted from hnRNP that contain snRNAs. We were able to obtain and purify ribonucleoproteins complexes containing some of the snRNAs. These particles (snRNPs) are very stable. They were purified by three different successive cycles of centrifugation under denaturing conditions. The particles are characterized by a density of 1,43 g/cm3 in CsCl and a sedimentation coefficient of 11--12S. They contain five species of snRNAs (U1, U2, U4, (U5), U6 according to the nomenclature of Lerner et al.) and at least one polypeptide with a molecular weight of about 15000 daltons. An other particle containing only U5 was also isolated. These snRNPs are not disaggregated in media destabilizing ionic forces, hydrophobic interaction or hydrogens bonds and seem to different from the snRNPs described by Lerner et al.