PROHIBITIN ANTIPROLIFERATIVE ACTIVITY AND LACK OF HETEROZYGOSITY IN IMMORTALIZED CELL-LINES

Experiments were performed to determine whether prohibitin, an evoluti onarily conserved gene with antiproliferative activity, has a role in cellular immortalization. A cell proliferation assay was used to exami ne one human cell line from each of four established immortal compleme ntation groups, termed A, B, C, and D, and a normal human diploid fibr oblast line. Only normal and Group B cells were inhibited from travers ing the cell cycle after introduction of wild-type prohibitin transcri pt. All of the immortalized cells expressed elevated levels of prohibi tin mRNA and protein. Prohibitin gene structural characterization usin g Southern and single-strand conformation polymorphism (SSCP) analyses distinguished two alleles. One is cleaved at a polymorphic intronic E coRI site, exhibits an exon 6-associated SSCP, and is homozygous only in Group B cells. The other is not cleaved at the EcoRI site, has a di fferent exon 6 SSCP pattern, and is homozygous in Groups A, C, and D. In contrast, normal cells are heterozygous for the alleles. These resu lts suggest that prohibitin may play a role as a tumor suppressor in t he immortalization of Group B cells. (C) 1995 Academic Press, Inc.