To ascertain that RNA degradation process is enzymatic and not chemically induced by various reactive compounds, yeast cells were fixed with 1% formaldehyde for 10 min or with 70% ethanol for 30 min prior to exposure to increasing concentrations of hydrogen peroxide ( Figure 3A and B) . Both fixation procedures preserve cellular structures, however, it is known that most fixatives have harmful consequences, e.g. cause some loss of cellular components, including ribosomes. Nevertheless, a similar approach had been used to demonstrate that DNA damage in apoptotic yeast cells was an enzymatic process (30) . Also, in the case of RNA, the appearance of specific H 2 O 2 -induced degradation products was prevented by fixation, although the overall level of rRNA was reduced. Some faster migrating RNA species were detected in formaldehyde or ethanol fixed cells, however, these were generated also in the absence of the oxidant and did not intensify after treatment ( Figure 3A and B, lane 4) .