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KMID : 1161519970010020363
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Animal Cells and Systems
1997 Volume.1 No. 2 p.363 ~ p.370
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Transcription and export of rnase mrp rna in xenopus laevis oocytes
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Jeong Sun-Joo
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Abstract
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RNase MRP is a ribonucleoprotein complex with a site?specific endonuclease activity. Its original substrate for cleavage is the small mitochondrial RNA near the mitochondrial DNA replication origin, thus it was proposed to generate the primer for mtDNA replication. Recently, it has been shown to have another substrate in the nucleus, such as pre?5.8S ribosomal RNA in nucleolus. The gene for the RNA component of RNase MRP (MRP RNA) was found to be encoded by the nucleus genome, suggesting an interesting intracellular trafficking of MRP RNA to both mitochondria and nucleolus after transcription in nucleus. In this study, genomic DNA encoding MRP RNA was microinjected into the nucleus of Xenopus oocytes, to analyze promoter regions involved in the transcription. It showed that the proximal sequence element and TATA box are important for basal level transcription; octamer motif and Sp1 binding sites are for elevated level transcription. Most of Xenopus MRP RNA was exported out to the cytoplasm following transcription in the nucleus. Utilizing various hybrid constructs, export of MRP RNA was found to be regulated by the promoter and the 5' half of the coding region of the gene. Interestingly, the transcription in nucleus seems to be coupled to the export of MRP RNA to cytoplasm. Intracellular transport of injected MRP RNA can be easily visualized by whole?mount in situ hybridization following microinjection; it also shows possible intra?nuclear sites for transcription and export of MRP RNA.
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KEYWORD
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RNase MRP, Transcription, RNA export, Xenopus, Microinjection, Mitochondria, Nucleolus, Whole-mount in situ hybridization
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