16S Mitochondrial Ribosomal RNA Degradation Is Associated with Apoptosis

The use of mitochondrial RNA as an indicator of apoptosis was investigated. Exposure of HA-1 fibroblastic cells to 10 H₂O₂ per 10⁷ cells induced nuclear fragmentation, cell shrinkage, and internucleosomal DNA fragmentation, all characteristics of apoptosis. RNA extracted from control and apoptotic cultures, and analyzed by Northern blot hybridization, revealed a significant increase in the degradation of mitochondrial 16S ribosomal RNA (rRNA) that was associated with apoptosis. Conversely, minimal, if any, degradation of glyceraldehyde-3-phosphate dehydrogenase or actin mRNAs was observed. Similar results were obtained for HA-1 cells treated with the protein kinase inhibitor staurosporine, and for HT-2 T-lymphocytes induced to undergo apoptosis by interleukin-2 withdrawal. In addition, 16S rRNA degradation was an early event that was discernable well before chromatin condensation in hydrogen peroxide-treated HA-1 cells. These observations suggest that degradation of mitochondrial 16S ribosomal RNA is a new marker of mammalian cell apoptosis. © 1997 Elsevier Science Inc.