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Different Rates of Synthesis and Turnover of Ribosomal RNA in Rat Brain and Liver
Author(s) -
Stoykova A. S.,
Dudov K. P.,
Dabeva M. D.,
Hadjiolov A. A.
Publication year - 1983
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1983.tb09038.x
Subject(s) - ribosomal rna , nucleolus , ribosome , rna , ribosome biogenesis , biology , cytoplasm , in vivo , 5s ribosomal rna , microbiology and biotechnology , biochemistry , gene , genetics
The kinetics of in vivo labeling of cellular free UMP and nucleolar, nucleoplasmic, and cytoplasmic rRNA with [ 14 C]orotate in rat brain and liver were investigated. Evaluation of the experimental data shows: (a) The rate of nucleolar precursors of ribosomal RNA (pre‐rRNA) synthesis and the deduced rate of ribosome formation in brain is about fivefold lower than in liver and corresponds to 220–260 ribosomes/min/nucleus. (b) The lower rate of in vivo pre‐rRNA synthesis is correlated with a lower activity of RNA polymerase I in isolated brain nuclei, (c) The half‐lives of nucleolar rRNA in brain and liver are 210 and 60 min, respectively, thus showing a slower rate of processing of pre‐rRNA in brain nucleoli. (d) The nucleo‐cytoplasmic transport of ribosomes in brain is also markedly slower than in liver and reflects the lower rates of synthesis and processing of pre‐rRNA. (e) Cytoplasmic ribosomes in brain and liver turn over with half‐lives of about 6 and 4 days, respectively. It is concluded that the markedly lower rate of ribosome biogenesis in brain is specified mainly at the level of transcription of rRNA genes.