A specialized processing body that is temporally and asymmetrically regulated during the cell cycle in Saccharomyces cerevisiae

Abstract

RNase mitochondrial RNA processing (MRP) is an essential ribonucleoprotein endoribonuclease that functions in the degradation of specific mRNAs involved in cell cycle regulation. We have investigated where this processing event occurs and how it is regulated. As expected, results demonstrate that RNase MRP is predominantly localized in the nucleolus, where it processes ribosomal RNAs. However, after the initiation of mitosis, RNase MRP localizes throughout the entire nucleus and in a single discrete cytoplasmic spot that persists until the completion of telophase. Furthermore, this spot was asymmetrically found in daughter cells, where the RNase MRP substrate, CLB2 mRNA, localizes. Both the mitotic exit network and fourteen early anaphase release pathways are nonessential but important for the temporal changes in localization. Asymmetric localization was found to be dependent on the locasome. The evidence suggests that these spots are specialized processing bodies for the degradation of transcripts that are cell cycle regulated and daughter cell localized. We have called these TAM bodies for temporal asymmetric MRP bodies.

Substrate recognition by ribonucleoprotein ribonuclease MRP

“…First, RNase MRP was shown to cleave the 59 UTR of the CLB2 (Cyclin B2) mRNA (Gill et al 2004). (RNase MRP, generally a nucleolar enzyme, was shown to transiently accumulate in a discrete cytoplasmic spot where it co-localizes with the CLB2 mRNA [Gill et al 2006]). In vitro cleavage assays performed on the 59 UTR of CLB2 mRNA confirm previously reported (Gill et al 2004) RNase MRP cleavage at sites that are consistent with the identified consensus (Supplemental Fig.…”

RNase MRP RNA and human genetic diseases

“…RNase MRP is also implicated in messenger RNA (mRNA) degradation and cell cycle progression at the end of mitosis. It processes the 5′-UTR of the cyclin B2 (CLB2) mRNA and regulates the completion of mitosis [8,9].…”

Interactions of a Pop5/Rpp1 heterodimer with the catalytic domain of RNase MRP

“…Yeast RNase MRP is also involved in the regulation of the cell cycle by cleaving the 59 UTR of cyclin B2 mRNA (Cai et al 1999(Cai et al , 2002Gill et al 2006). Defects in RNase MRP function result in a variety of recessive pleiotropic diseases typically characterized by dwarfism (Ridanpaa et al 2001;Thiel et al 2005;Martin and Li 2007;Glazov et al 2011); the mechanisms responsible for the development of these diseases are not known.…”

“…RNase MRP is essential for the viability of eukaryotes (Schmitt and Clayton 1992;Schneider et al 2010). Though it was originally identified as a mitochondrial enzyme, the vast majority of RNase MRP is found in the nucleolus and, transiently, in the cytoplasm (Chang and Clayton 1987a;Karwan et al 1991;Gill et al 2006, and references therein). Mitochondrial RNase MRP has a distinct protein composition which is yet to be fully characterized (Lu et al 2010) and will not be discussed in this study.…”