A Study of the Possible Role of Transfer RNA in the Regulation of Enzyme Synthesis in Neurospora

Citation

Shearn, Allen David (1969) A Study of the Possible Role of Transfer RNA in the Regulation of Enzyme Synthesis in Neurospora. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/9TVD-N609. https://resolver.caltech.edu/CaltechTHESIS:03282017-143303527

Abstract

In several organisms, developmental transitions are accompanied by transfer RNA (tRNA) alterations. These alterations are usually observed in the chromatographic profile of amino acyl-tRNA specific for one or more amino acids and are of interest because of their possible significance in the regulation, at the translation level, of specific protein synthesis and cell differentiation. I have investigated whether such alterations accompany the biochemical differentiation of vegetative cultures of Neurspora crassa which occurs in response to "hard-times," e.g., starvation or inhibition by amino acid analogs or cycloheximide. The synthesis of tyrosinase is a well-known characteristic of this developmental transition.

After determining the conditions required for the complete charging of all 20 amino acids to Neurospora tRNA, I compared the chromatographic profile on methylated albumin-Kieselguhr columns of amino acyl-tRNA's from vegetative cultures to those of cultures which were derepressed for tyrosinase with ethionine, a methionine analog. No qualitative tRNA alterations were observed; the same number of components for each amino acid were found in cultures of both developmental states and they had the same chromatographic mobilities. However, quantitative changes of acceptor activity were observed for several amino acids. The time course of the pattern of quantitative alteration suggests that the observed changes result from partial ribonuclease digestion of the tRNA complement. I believe this ribonuclease is synthesized in response to the deprived environment and its function is to hydrolyze the RNA which is present in excess, in order that the catabolic products may be used as building blocks for the synthesis of other kinds of molecules.

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