RNA Metabolism in Mammalian Cells at Elevated Temperature

RNA synthesis and metabolism were investigated in Hela cells heated to 42°. At this temperature celluar growth is arrested. After prolongued periods of preheating the initial rate of uridine incorporation into RNA is only slightly affected but no new stable RNA accumulates. After a shift down to 37° the normal pattern of RNA formation resumes.45 S precursor to rRNA is still formed but its normal metabolism to functional rRNA is blocked. No new rRNA appears in cytoplasmic ribosomes. On the contrary, the synthesis of nascent messenger‐like RNA is only slightly affected and non‐ribosomal RNA appears in the cytoplasm at a normal rate. The temperature sensitive event seems thus to be selectively located in the metabolic chain producing functional rRNA.