Inhibition of translation and cell growth by minigene expression

A random five-codon gene library was used to isolate minigenes whose expres sion causes cell growth arrest, Eight different deleterious minigenes were isolated, five of which had in-frame stop codons; the predicted expressed p eptides ranged in size from two to five amino acids, Mutational analysis de monstrated that translation of the inhibitory minigenes is essential for gr owth arrest. Pulse-labeling experiments showed that expression of at least some of the selected minigenes results in inhibition of cellular protein sy nthesis. Expression of the deleterious minigenes in cells deficient in pept idyl-tRNA hydrolase causes accumulation of families of peptidyl-tRNAs corre sponding to the last minigene codon; the inhibitory action of minigene expr ession could be suppressed by overexpression of the tRNA corresponding to t he last sense codon in the minigene. Experimental data are compatible with the model that the deleterious effect of minigene expression is mediated by depletion of corresponding pools of free tRNAs.