Ribosomal RNA synthesis in mitochondria of Neurospora crassa |
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Authors: | Y Kuriyama D J Luck |
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Affiliation: | Laboratory of Cell Biology The Rockefeller University New York, N.Y. 10021, U.S.A. |
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Abstract: | Ribosomal RNA synthesis in Neurospora crassa mitochondria has been investigated by continuous labeling with [5-3H]uracil and pulse-chase experiments. A short-lived 32 S mitochondrial RNA was detected, along with two other short-lived components; one slightly larger than large subunit ribosomal RNA, and the other slightly larger than small subunit ribosomal RNA. The experiments give support to the possibility that 32 S RNA is the precursor of large and small subunit ribosomal RNA's. Both mature ribosomal RNA's compete with 32 S RNA in hybridization to mitochondrial DNA. Quantitative results from such hybridization-competition experiments along with measurements of electrophoretic mobility have been used to construct a molecular size model for synthesis of mitochondrial ribosomal RNA's. The large molecular weight precursor (32 S) of both ribosomal RNA's appears to be 2.4 × 106 daltons in size. Maturation to large subunit RNA (1.28 × 106 daltons) is assumed to involve an intermediate ~1.6 × 106 daltons in size, while cleavage to form small subunit RNA (0.72 × 106 daltons) presumably involves a 0.9 × 106 dalton intermediate. In the maturation process ~22% of the precursor molecule is lost. As is the case for ribosomal RNA's, the mitochondrial precursor RNA has a strikingly low G + C content. |
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