The effect of essential amino acid deprivation on poly(A) metabolism in Neurospora crassa.

Poly(A) messenger RNa was isolated from a methionine auxotroph of Neurospora crassa grown to exponential and early stationary phases, and from mycelia deprived of the essential amino aid. The polyadenylate regions were isolated from the mRNA preparations by enzymatic digestion and affinity chromatography, and their lengths determined by electrophoresis on 10% acrylamide/90% formamide gels. There was no significant difference in the lengths of the poly(A) regions between exponential and early stationary phase cultures. However, the poly(A) regions of mRNA isolated from cells undergoing amino acid deprivation were larger and more heterogeneous than the poly(A) regions isolated from cells grown in amino acid-supplemented medium. Whole cell extracts prepared from both amino acid-supplemented and amino acid-deprived cultures were assayed for their ability to synthesize and degrade poly(A). No significant difference between the two extracts was detected in either poly(A) polymerase or poly(A)-degrading activities. It was concluded that continuing translational activity in required for the shortening of poly(A) tracts in N. crassa.