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.