Mammalian RNA polymerases I and II: Independent diurnal variations in activity

Stanley R. Glasser, Thomas C. Spelsberg

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


Diurnal variations in the activities of nucleolar (I) and non-nucleolar (II) DNA-dependent RNA polymerases of rat liver were observed. Both polymerase I and II displayed diphasic shifts in activity levels. However, the patterns of the individual shifts were not synchronous. Polymerase I activity was highest between 0100-1100 hours and lowest between 1700-2000 hours while polymerase II peaks between 2400 and 0500 hours with a low point at 1000 hours. The daily fluctuations and the dissimilar patterns of polymerase I and II activity may be of such significance as to require reevaluation and redesign of studies dealing with regulation of enzyme activity.

Original languageEnglish (US)
Pages (from-to)951-958
Number of pages8
JournalBiochemical and Biophysical Research Communications
Issue number4
StatePublished - May 26 1972

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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