Ultrastructural detection of cellular and viral RNA with biotinylated DNA probes

We describe a procedure for detecting and localizing cellular rRNA and HIV virus RNA, based on in situ hybridization at the ultrastructural level. After contact with ultrathin sections of cells embedded in Lowicry K4M, biotinylated DNA probes yield specific hybrids identified by a colloidal gold immunocytochemistry marker. The cellular transcripts are preferentially located in the ribosome structures of the cytoplasme and in the dense fibrillar component of the nucleolus. With the HIV probe, viral RNA molecules, were observed over infected cell and some extracellular viral particles. In the cytoplasm the hybridization signal is detected frequently at the periphery close to the plasma membrane, whereas the gold signal associated with virions is localized mainly over the center (core) of the particle.