Effects of nitrogen starvation on "stable" RNA synthesis in Rhodotorula gracilis cells

In exponentially growing cells of Rhodotorula gracilis, transferto a nitrogen-free medium causes the acceleration of RNA breakdownprocesses and the arrest of the synthesis of 5 s and 4 s RNA,followed by a progressive fall in the formation of mature rRNAspecies. At the same time, the accumulation of protein graduallydecreases, and the final block corresponds to the block of theaccumulation of rRNA. Labelling experiments suggest that theprogressive arrest of the formation of mature rRNA species depends,at least to a good extent, on the breakdown of the newly-synthesizedrRNA precursor due to hypomethylation of the molecule. The possiblerelationship between the level of amino acids and the synthesisof 5 s and 4 s RNA is discussed. (Received April 22, 1976; )