Ultraviolet light-induced crosslinking of two major phosphoproteins and poly(A)+RNA from free polyribosomes; changes in phosphorylation by inhibitors of transcription and translation.

Polyribosomes were isolated without the use of detergents, irradiated with ultraviolet light and labelled in the presence of (gamma-32P) adenosine 5'-triphosphate. Poly(A)+RNA-protein structures separated by chromatography on oligo (dT)-cellulose contained up to 1o crosslinked proteins as shown by SDS-polyacrylamide gel electrophoresis. These included a 71 kDa poly(A)-bound species and two major phosphoproteins of 66 and 13o kDa. Pretreatment of rats with inhibitors of transcription and translation caused different and significant alterations in the labelling of the two phosphoproteins, suggesting that phosphorylation of proteins closely associated with mRNA may be involved in the regulation of the stability of this RNA or its binding to structural elements in the cell.