Ribosome Biogenesis and Nucleolar Ultrastructure in Neuronal and Oligodendroglial Rat Brain Cells

Abstract

The absolute amounts of precursor to ribosomal RNA (pre-rRNA) and ribosomal RNA (rRNA) in isolated rat brain neuronal and oligodendroglial nuclei were determined. The amount of the major pre-rRNA and rRNA species in neuronal nuclei was about twofold higher than in oligodendroglial nuclei. The relative rate of pre-rRNA synthesis in vivo was 2.3- to 2.7-fold higher in neuronal as compared with oligodendroglial nuclei. This corresponds to a 2.7-fold higher activity of the "template-bound" RNA polymerase I in isolated neuronal nuclei, whereas the activity of the "free" enzyme in both neuronal and glial nuclei was almost identical. The higher transcription rates of rRNA genes correlated with the markedly more prominent fibrillar component in neuronal nucleoli. The turnover times of the major pre-rRNA and rRNA species in neuronal and oligodendroglial nuclei were similar, except for 45S pre-rRNA, which turned over at an approximately 1.5-fold slower rate in neuronal nuclei. The relative rates of processing of pre-rRNA and of nucleocytoplasmic transport of rRNA in neuronal cells were approximately 2.7-fold higher than in oligodendroglial cells and corresponded to the differences in rRNA gene transcription rates. The established ribosome formation features correlated with an abundant (neurons) or exceedingly scarce (oligodendrocytes) nucleolar granular component. The turnover rate of cytoplasmic ribosomes in rat brain neurons was twofold slower than in oligodendrocytes, largely because of the about fivefold higher amount of ribosomes in the cytoplasm of neurons. We conclude that ribosome formation and turnover in neuronal and oligodendroglial cells are adapted to the protein synthetic levels in these two types of brain cells.

Dynamically committed, uncommitted, and quenched states encoded in protein kinase A revealed by NMR spectroscopy

“…This difference in affinity is amplified by ADP to 40 times, reflecting the strong cooperative effect between PKI and nucleotide (15,16). Remarkably, PKI [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and PLN [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] have different thermodynamics of binding (Fig. 1A).…”

“…To compare the effects of binding substrates and inhibitors to PKA-C, we synthesized two peptides: the first peptide corresponding to the cytoplasmic domain of phospholamban (PLN 1-20 ), an endogenous inhibitor for the sarcoplasmic reticulum Ca-ATPase and native substrate of PKA-C in cardiac muscle (14); and the second peptide corresponding to PKI [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] (Fig. S1).…”

“…Here, we examined the effects of inhibitors on the conformational dynamics of the enzyme: a competitive peptide inhibitor corresponding to the inhibitory region of PKI (PKI 5-24 ) (8) and magnesium, which under high concentrations behaves kinetically as a noncompetitive inhibitor of PKA-C (9, 10). The combination of high Mg 2þ concentrations with PKI has implications for the cellular control of PKA-C activity to arrest transcription during mitosis (11,12). By comparing the results with those obtained in the presence of a peptide substrate (7) which competes with PKI 5-24 at the binding groove of PKA-C, we found that both PKI [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and excess Mg 2þ restrict the enzyme dynamics on a fast (picosecond to nanosecond) and slow (microsecond to millisecond) NMR timescale without drastically changing the conformation of the ternary complex.…”

Targeting of CTCF to the nucleolus inhibits nucleolar transcription through a poly(ADP-ribosyl)ation-dependent mechanism

“…The blockage of protein synthesis can be achieved with cycloheximide (Chx); it leads to a rapid depletion of short half-life transcription factors of the RNA polymerase I complex and inhibition of rDNA transcription and pre-rRNA processing (Gokal et al, 1986;Stoykova et al, 1985). In these experiments, UR61 cells were transfected with GFP-CTCF or GFP-ZF constructs and, 24 hours post-transfection, treated with Chx for 3 hours (Fig.…”

Analysis of the role of RNS2 and autophagy in the turnover of ribosomal RNA in Arabidopsis thaliana

“…This may be because RNautophagy only operates in certain tissues within the leaf. LAMP2C, for example, is highly expressed in neurons, which are rich in RNA and a disequilibrium in these cells can lead to disease (Stoykova et al 1985;Gray and Woulfe 2013). When the RNA component of Alexa488 is removed, overall vacuole fluorescence was reduced indicating that the transport process is selective for RNA.…”