ADP-ribosylation of heterogeneous ribonucleoproteins in HeLa cells

Poly and mono (ADP-ribosyl)transferases catalyze the transfer of ADP-ribose from nicotinamide adenine dinucleotide (NAD) to acceptor proteins. Protein substrates of ADP-ribosylation reactions were investigated in human cervical carcinoma (HeLa) cells in the exponential phase of growth. Permeabilized cells were incubated with [32P]-NAD and ADP-ribosylated proteins were detected by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and autoradiography. Microsequencing of two coomassie blue-stained proteins corresponding to 32P-labeled proteins on autoradiographs revealed sequence identity with heterogeneous ribonucleoproteins (hnRNPs) A1 and A2/B1, consistent with the isoelectric points, molecular sizes, and 2D-PAGE map locations of these proteins. ADP-ribosylation of hnRNPs may thus serve to modulate the activity of these proteins in the nucleus.