AJP - Cell Physiology, Vol 253, Issue 4 C506-C513, Copyright © 1987 by American Physiological Society
Regulation of ribosome synthesis during compensatory renal hypertrophy in mice
A. J. Ouellette, R. Moonka, A. D. Zelenetz and R. A. Malt
Cell Biology Unit, Shriners Burns Institute, Massachusetts General Hospital, Boston.
Ribosomal synthesis was studied at the transcriptional and translational
levels to investigate the mechanisms of ribosome accretion during
compensatory renal hypertrophy. As measured by in vitro transcriptional
runoff comparisons 6-48 h after surgery, nuclei from the kidney remaining
after contralateral nephrectomy show an increase of up to 150% in the rate
of synthesis of ribosomal precursor RNA. The rate of rDNA transcription is
40-50% greater than control values as early as 6 h after nephrectomy; by 48
h, the rate returns to normal. In contrast to the stimulated transcription
of rDNA and accretion of rRNA, the steady-state levels and the cytoplasmic
distribution of ribosomal protein mRNAs S16 and L10 remain unchanged during
induced renal growth. Thus coordinate production of adequate protein for
increased assembly of ribosomes during induced renal growth appears to be
accomplished by increasingly efficient translation of existing ribosomal
protein mRNAs or by post-translational stabilization of ribosomal proteins.
The rate of rDNA transcription may be regulated by accelerating the
transcription of already functioning genes or, more likely, by recruiting
transcription units that are transcriptionally inactive in the normal
kidney.
