16S MITOCHONDRIAL RIBOSOMAL-RNA DEGRADATION IS ASSOCIATED WITH APOPTOSIS

The use of mitochondrial RNA as an indicator of apoptosis was investig ated. Exposure of HA-1 fibroblastic cells to 10 mu mol H2O2 per 10(7) cells induced nuclear fragmentation, cell shrinkage, and internucleoso mal DNA fragmentation, all characteristics of apoptosis. RNA extracted from control and apoptotic cultures, and analyzed by Northern blot hy bridization, revealed a significant increase in the degradation of mit ochondrial 16S ribosomal RNA (rRNA) that was associated with apoptosis . Conversely, minimal, if any, degradation of glyceraldehyde-3-phospha te dehydrogenase or actin mRNAs was observed. Similar results were obt ained for HA-1 cells treated with the protein kinase inhibitor stauros porine, and for HT-2 T-lymphocytes induced to undergo apoptosis by int erleukin-2 withdrawal. In addition, 16S rRNA degradation was an early event that was discernable well before chromatin condensation in hydro gen peroxide-treated HA-1 cells. These observations suggest that degra dation of mitochondrial 16S ribosomal RNA is a new marker of mammalian cell apoptosis. (C) 1997 Elsevier Science Inc.