THE MESSENGER-RNAS FOR CYCLIN-A, C-MYC AND RIBOSOMAL-PROTEINS L4 AND S6 ARE ASSOCIATED WITH CYTOSKELETAL-BOUND POLYSOMES IN HEPG2 CELLS

Cytosolic, cytoskeleton and membrane fractions were extracted from Hep G2 cells by a sequential detergent/salt extraction procedure. The cyto solic fraction contained 93% of the lactic dehydrogenase activity whil e the cytoskeleton fraction was enriched in action and vimentin. The d istribution of mRNAs for c-myc, glucose transporter 1, ribosomal prote ins L4 and S6 and cyclin A were investigated by Northern hybridization of total RNA extracted from polysomes isolated from cytosolic, cytosk eleton and membrane fractions. The membrane-bound polysomes were enric hed in the glucose transporter 1 mRNA and the cytoskeleton-bound polys omes were enriched in the mRNAs for the two ribosomal proteins, c-myc and cyclin A. The results suggest that the mRNAs for nuclear proteins are one class of mRNAs which are translated on polysomes associated wi th the cytoskeleton; this may be related to the requirement to transpo rt the newly synthesized protein to the nucleus.