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Editorials |
Department of Cellular Pathology, Armed Forces Institute of Pathology, Washington, DC 20306-6000, Fax 202-782-7623, E-mail oleary@afip.osd.mil
Rapid degradation of RNA is the most important factor impeding the analysis of gene expression in human cells and tissues. Once a tissue has been removed from its normal environment, the relative rates of RNA synthesis and degradation change. This in turn gives rise to changes in the relative proportions of various RNA species within a tissue, as well as to an overall reduction of RNA concentrations.
Several approaches have been used to reduce the rate at which RNA
concentrations decline after tissue collection. Contamination of
samples with exogenous ribonucleases (RNases), particularly those used
in the laboratory during RNase treatment of DNA isolates, is
universally recognized as an important cause of RNA loss. The use of
meticulous laboratory technique to reduce this contamination is
absolutely essential to preserve RNA substrates, but is not sufficient
to permit analysis of all RNA targets. Isolation of RNA, along with the
use of RNase inhibitors, such as diethyl pyrocarbonate, or chaotropic
agents, such as guanidinium chloride or guanidinium isothiocyanate,
often used in combination, is also helpful, but also is laborious and
time-consuming. Rapid fixation of tissue samples with neutral-buffered
formalin or precipitating agents, such as ethanol, destroys RNase
activity, but increases the complexity of RNA isolation and may inhibit
polymerase
References
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