Structural investigation of nuclear RNP particles containing pre-mRNA by different fluorescenc techniques

Abstract

Ethidium bromide (EB) adsorption isotherms on 30S nuclear RNP particles isolated from liver nuclei has revealed 6% of double-stranded regions in pre-mRNA (dsRNA). It has been established by measurements of the EB fluorescence polarization that the bulk of dsRNA regions in RNP is rigidly attached to RNP. They are longer than 45 degree A. The increase of NaCl concentration from 0.1 up to 0.4 M causes a significant loosening of dsRNA-protein bonds. As a result the dsRNA segments become more flexible. Measurements of energy transfer from fluorescamine (covalently bound to the protein) to EB (adsorbed on dsRNA) have yielded information about dsRNA location. The fact that absorbtion of exciting light by fluorescamine causes pronounced increase of EB fluorescence is consistent with the idea that helical regions of RNA are located outside the RNP particles.

Heterogeneous nuclear ribonucleoproteins (hnRNPs) in cellular processes: Focus on hnRNP E1's multifunctional regulatory roles

“…These activities have been used to develop several different models to explain how hnRNPs function (Conaway and Conaway 1988). The first model developed from the observation that metazoan hnRNPs are found in large complexes with pre-mRNAs when examined by electron microscopy (Borissova et al 1981). These nucleosome-like structures have been referred to as ribonucleosomes, indicating that their main function was in the packaging of premRNAs.…”

hnRNP particles

“…RNA melted on the surface of particles. Some remaining secondary structure was most likely from the part of hnRNA connecting with the neighbouring particles (22) (Fig. 3).…”