[Nuclear RNP containing pre-mRNA. 16. Cross-linked informofers]

The proteins of 30S RNP particles containing pre-mRNA (hnRNA) were cross-linked with bifunctional reagents (dimethylsuberimidate and dimethyl-3,3'dithiobispropionimi-date). Further treatment with 1 or 2 M NaCl dissociates all RNA from protein. However, a significant part of protein particles--informofers, being cross-linked survived high salt treatment. Their sedimentation coefficients were close to those of original particles. No RNA could be detected in the informofers even after labeling the cells with a precursor for a long period of time. Sodium dodecylsulfate or urea dissociated cross-linked informofers into oligomeric polypeptides. They could be dissociated by beta-mercaptoethanol treatment if a reversible cross-linking reagent has been used. The resulting polypeptides were represented by informatin. RNP particles (30S RNP or polyparticles) were reconstituted upon mixing or cross-linked informofers with pre-mRNA and removal of 2 M NaCl. The reconstituted particles were indistinguishable from the original ones by several tests.