J. Delic et al., GAMMA-RAY-INDUCED TRANSCRIPTION AND APOPTOSIS-ASSOCIATED LOSS OF 28S RIBOSOMAL-RNA IN INTERPHASE HUMAN-LYMPHOCYTES, International journal of radiation biology, 64(1), 1993, pp. 39-46
Citations number
36
Categorie Soggetti
Radiology,Nuclear Medicine & Medical Imaging","Nuclear Sciences & Tecnology
Apoptosis, related to a naturally-occurring or programmed cellular dea
th process, can be physiologically or exogenously induced. In vertebra
te cells undergoing apoptosis, initiated by any of these ways, one of
the numerous biochemical changes is an endogenous endonuclease activat
ion that cleaves the chromatin DNA into oligonucleosome-sized 'ladder'
fragments. In the present study we show that in parallel to chromatin
DNA cleavage, ribosomal RNA is lost in gamma-ray-mediated apoptotic h
uman lymphocytes. We demonstrate that 28S rRNA gene transcription is i
nduced early (15 min) after irradiation, followed by a selective disap
pearance in apoptotic cells only. The fact that newly synthesized rRNA
turns over at the same rate in irradiated and untreated cell fraction
s, highly suggests that the observed loss of 28S rRNA in the apoptotic
cell fraction at the ribosome level is due to degradation occurring a
t a late stage of the apoptotic death process. These results suggest t
hat, in addition to first-stage apoptosis-associated rDNA gene activat
ion, cellular self-destruction at late stages is associated with proce
sses occurring simultaneously at the ribosome level involving an endog
enous RNase-like activity, and at the chromatin level involving DNA-nu
clease activity.