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Multiple species of bovine adrenodoxin mRNA. Occurrence of two different mitochondrial precursor sequences associated
Abstract:
Bovine adrenodoxin mRNA is found to consist of several distinct mRNA species which can be divided into two sets. Each set utilizes at least three of four separate poly(A)+ addition sites providing an explanation of the three sizes of adrenodoxin mRNA (1.75, 1.4, and 0.95 kilobases) previously observed in bovine adrenocortical RNA by this laboratory (Okamura, T., John, M.E., Zuber, M.X., Simpson, E.R., and Waterman, M.R. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 5705-5709). The two sets are distinguished from one another by a unique 5' sequence leading to two different amino acid sequences (approximately 10% homology) for the precursor portion of this nuclear encoded, mitochondrial protein. A common mature adrenodoxin sequence is encoded by both sets of mRNA. One set of RNAs is 10-fold more abundant than the other, but the levels of both sets can be induced by treatment of primary bovine adrenocortical cell cultures with adrenocorticotropin. The biological significance of these two types of adrenodoxin precursor sequences remains obscure.
Insights
Two bovine adrenodoxin mRNA sets explain observed sizes and yield distinct precursor proteins. Both sets produce common mature adrenodoxin and are induced by adrenocorticotropin.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Bovine adrenodoxin mRNA exhibits multiple size variants (1.75, 1.4, 0.95 kilobases).
- Previous research identified these distinct mRNA sizes in bovine adrenocortical RNA.
Purpose of the Study:
- To investigate the molecular basis of bovine adrenodoxin mRNA size heterogeneity.
- To characterize the distinct mRNA species and their encoded protein sequences.
Main Methods:
- Analysis of bovine adrenodoxin mRNA species.
- Identification of poly(A)+ addition sites.
- Comparison of 5' sequences and encoded amino acid sequences.
Main Results:
- Bovine adrenodoxin mRNA comprises two distinct sets, each using multiple poly(A)+ sites.
- These sets generate different precursor protein sequences (10% homology) but a common mature adrenodoxin.
- One mRNA set is 10-fold more abundant and both are inducible by adrenocorticotropin.
Conclusions:
- The two mRNA sets explain the observed adrenodoxin mRNA sizes and precursor diversity.
- The biological significance of the distinct precursor sequences is currently unknown.