Molecular Biology

Cytosolic rRNAs are highly dynamic and can be degraded under conditions such as apoptosis, starvation and magnesium depletion. The degradation is also related to their specific localization, as fractions of cytosolic ribosomes are localized on the surfaces of intracellular organelles, such as endoplasmic reticulum (ER) and mitochondria. Such localized translation facilitates translocation of nascent proteins into these organelles co-translationally, contributing to fast responses to cellular stresses and precise regulations of the organelle. Here, we describe a protocol to establish the in organello system to investigate rRNA degradation on mitochondrial outer membrane or ER. The protocol consists of organelle isolation, rRNA degradation on organelles and agarose gel electrophoresis to examine the remaining rRNAs.

The RNA exosome complex plays a central role in RNA processing and regulated turnover. Present both in cytoplasm and nucleus, the exosome functions through associations with ribonucleases and various adapter proteins (reviewed in [Kilchert et al., 2016]). The RNA exosome-associated EXOSC10 protein is a distributive, 3’-5’ exoribonuclease. The following protocol describes an approach to monitor the ribonucleolytic activity of affinity-purified EXOSC10-containing RNA exosomes, originating from HEK-293 cells, as reported in (Domanski et al., 2016) and further detailed in the companion bio-protocol to this one (Domanski and LaCava, 2017).

The RNA exosome complex plays a central role in RNA processing and regulated turnover. Present both in cytoplasm and nucleus, the exosome functions through associations with ribonucleases and various adapter proteins (reviewed in [Kilchert et al., 2016]). The following protocol describes an approach to purify RNA exosome complexes from HEK-293 cells, making use of inducible ectopic expression, affinity capture, and rate-zonal centrifugation. The obtained RNA exosomes have been used successfully for proteomic, structural, and enzymatic studies (Domanski et al., 2016).