EFFECTS OF TEMPERATURE ON THE PATTERN OF RNA SYNTHESIS IN XENOPUS LAEVIS NEURULA CELLS

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Abstract
Isolated cells of X. laevis neurulae were labeled with 3H-uridine at 3 different temperatures (21.degree., 30.degree. and 10.degree. C), and the pattern of RNA synthesis was examined, using polyacrylamide gels. At 21.degree. C (standard temperature), synthesis of 28S and 18S rRNA and other RNA, occurred quite actively. At 30.degree. C (higher temperature), the syntheses of rRNA, 4S and heterogeneous RNA were all increased about 2-fold (Q10 = 2). When the temperature was lowered to 10.degree. C, however, accumulation of 28S and 18S rRNA was inhibited nearly completely, while other RNA were still synthesized at a 50% level. The absence of 40S rRNA precursor at 10.degree. C makes it highly likely that at the lowered temperature the transcription of rRNA precursor is inhibited. These effects of temperature changes on RNA synthesis were all reversible: the synthesis returned to a normal rate within 4 h in those cells that had previously been exposed to the lower or higher temperature for 6 h.