Statin, a nonproliferation-specific protein, is associated with the nuclear envelope and is heterogeneously distributed in cells leaving quiescent state.
Statin, a protein of 57,000 daltons, is present primarily in the nuclei of nonproliferating cells of terminally differentiated tissues or of in vitro aged fibroblast cultures. In young growing cells, the protein can be induced to appear in the nuclei once the cell-cycle traverse is blocked by various tissue culture manipulations, such as serum starvation; this expression, however, can be rapidly removed by addition of serum. The disappearance of statin in cells leaving the quiescent state is not uniform along the periphery of the nucleus; it can be distributed in various patterns, such as caps, nodules, patches, or irregular granules. This unusual distribution seems to suggest that preferential sites exist at the region of the nuclear envelope where statin presence may residually remain. The concentration of statin at the nuclear envelope region in cells at G0-quiescent phase is confirmed by the intense staining of fluorescent antibody at the periphery of isolated rat liver nuclei. Further examination of the isolated nuclei reveals that the protein is associated with the lamina compartment of the nuclear envelope; this is evidenced by the results of immunoblotting experiments showing statin presence in the fraction enriched for lamins A-C. Immunogold labelling studies show that the protein is located in the general area of the nuclear envelope. These results suggest that statin in G0-quiescent cells is located predominantly at the nuclear envelope region and that in this vicinity there may exist geometrically sites of statin concentration as evidenced by the heterogeneous distribution in those cells experiencing the departure from the quiescent state.
Wang
E
E
Bloomfield Centre for Research in Aging, Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, Montréal, Québec, Canada.
D000818:Animals; D002451:Cell Compartmentation; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002460:Cell Line; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D008970:Molecular Weight; D009685:Nuclear Envelope / Q000502:physiology*; D009687:Nuclear Proteins; D020648:Peptide Elongation Factor 1; D011506:Proteins / Q000502:physiology*; D051381:Rats
D018797:Cell Cycle Proteins; C503234:EEF1A2 protein, human; D009687:Nuclear Proteins; D020648:Peptide Elongation Factor 1; D011506:Proteins