Fractionation of nucleolar proteins by two-dimensional gel electrphoresis

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 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 identifieid. 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 30000-70000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.