Fractionation of nucleolar proteins by two-dimensional gel electrophoresis

Isolation of nucleolar proteins was obtained by dissociation in the presence of urea – guanidine hydrochloride, followed by high-speed centrifugation to remove nucleic acids. At least 31 fractions of nucleolar proteins were detected by isoelectrofocusing gel electrophoresis in the pH range 3.5–10. Following two-dimensional gel electrophoresis on sodium dodecyl sulfate – polyacrylamide slab gels, more than 100 components of nucleolar proteins were identified. Two-thirds of nucleolar proteins were located in the pH range 5–8 following isoelectrofocusing. The molecular weights of these classes of proteins were shown to be mostly 30 000 – 70 000 by sodium dodecyl sulfate – polyacrylamide gel electrophoresis.