DISTRIBUTION OF RNASE MRP RNA DURING XENOPUS-LAEVIS OOGENESIS

RNase MRP is a ribonucleoprotein endoribonuclease found predominantly in nucleoli, but which has been associated with mitochondria and mitoc hondrial RNA processing. In order to analyze the intracellular localiz ation of specific RNA components of ribonucleoproteins of this type, a whole-mount method for in situ hybridization in Xenopus laevis oocyte s was employed. Results with specific probes (for both mitochondrial a nd nonmitochondrial RNAs) indicate that this procedure is generally ef fective for the detection of a variety of nucleic acids that reside in different cellular compartments. Probes used to detect the endogenous RNA component of RNase MRP (MRP RNA) during X. laevis oogenesis revea led a continuous nuclear signal as well as a possible dual localizatio n of MRP RNA in nucleoli and mitochondria at developmental stages temp orally consistent with both ribosomal and mitochondrial biogenesis. Ge nomic DNA encoding MRP RNA was injected into the nuclei of stage VI oo cytes and correctly transcribed. The in vivo-transcribed RNA was prope rly assembled with at least some of its cognate proteins as demonstrat ed by immunoprecipitation with specific autoantiserum. In addition, de tectable levels of the RNA were exported to the cytoplasm. This wholem ount procedure has permitted us to identify MRP RNA in situ at differe nt developmental time points as well as during transcription of the in jected gene, and suggests differential localization of MRP RNA during oogenesis consistent with its proposed function in both mitochondria a nd nucleoli. (C) 1995 Wiley-Liss, Inc.