Defect in polyamine metabolism in a BHK cell mutant temperature‐sensitive for rRNA maturation

A mutant of BHK cells (ts422E) temperature-sensitive for processing 32S rRNA to 28S rRNA (Toniolo et al., '73) also loses the ability to synthesize polyamines and 5.8S rRNA when shifted to the non-permissive temperature (39 degrees). The activity of several enzymes not involved with polyamine synthesis, methylation of 32S rRNA, and small nuclear RNA production are apparently unaffected after at least 24 hours at 39 degrees. When cultures are returned to the permissive temperature (33 degrees), polyamine synthesizing capacity returns to normal as mature rRNA production resumes.