Stability of nuclear RNA in mammalian cells (original) (raw)
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Stabilities of Nuclear and Messenger Rna Molecules in Sea Urchin Embryos
Journal of Cell Biology, 1972
The kinetics of accumulation of radioactive adenosine in adenosine triphosphate and in RNA of nuclear, cytoplasmic, and polysomal fractions of sea urchin embryos have been analyzed. 85% of the RNA synthesized decays in the nucleus with an apparently uniform half-life of about 7 min. The remaining 15% goes to the cytoplasm, mostly entering polysomes, and decays with a quite uniform half-life of about 75 min. The nuclear RNA accounts for one-third and the cytoplasmic RNA accounts for two-thirds of the total unstable RNA which accumulates at steady state in the embryo. The size distribution of shortlabeled nuclear RNA is very similar to that of long-labeled messenger RNA, when both are extracted directly from the cells without a previous cell fractionation .
The role of nuclear proteins in RNA synthesis
Experimental Cell Research, 1972
When epithelial cells from baby mice are cultured on a solid substrate in vitro, DNA synthesis and cell division take place in a majority of the cells 24 to 48 h after inoculation. This cell proliferation is regularly preceded by a sequence of nuclear changes likely to be involved in gene activation during the process of growth-transformation. These nuclear changes, which in the present investigation were studied by quantitative cytochemical methods, are characterized by: (1) increased binding of acridine orange (AO) very soon after cell attachment, reflecting initial changes of the deoxvribonucleoprotein (DNP) complex: (2) accumulation of uroteins in the cell nucl&s; (3) dispersion of the nuclear cdromatin; (4) increased rate of 14C-uridine incorporation. The initial DNP change. reflected by the increased AO-binding, was per se not a sufficient factor for stimulation of-14C-uridine incorporation. An increasedgH-uridine incorporation was only observed when protein began to accumulate in the nucleus and when the chromatin changed from a condensed to a more dispersed state. The rate of 14C-uridine incorporation was, during the whole process of growth transformation, found to be directly proportional to the amount of protein that had accumulated in the nucleus. However, the initial DNP change was a necessary prerequisite for the subsequent accumulation of protein in the nucleus. Attachment of the cells to the solid substrate was found to be necessary in expressing this sequence of nuclear events. Furthermore, in areas on the glass slide where many cells had attached, these nuclear changes occurred more rapidly.
Some features of nucleo-cytoplasmic RNA transport from isolated nuclei
Molecular Biology Reports, 1981
Messenger RNA is released preferentially from isolated rat liver nuclei in the presence of the ATPgenerating system and cytosol. The release is suppressed by spermidine, while cytoplasmic RNase inhibitor was ineffective and PCMB like some other thiol-blocking agents inhibitory. Cytoplasmic SOD added to the system strongly suppressed RNA release. A similar effect could be obtained by anaerobiosis due to addition of SMP. In both cases the inhibition is reversed by cyanide.
Cell, 1974
The stabllities of the principal classes of RNA have been studfed in resting and exponentially growlng mouse fibroblast lines 3T6 and 3T3. Cytoplasmic mRNA, labeled with tritfated uridine and isolated by virtue of its poly A content, is equally stable in resting and growing cells, displaying a half-life of about 9 hr. We conclude that the accumuiatlon of poly A(+) mRNA during transition from resting to growtng state is due not to an increase in its stability, but to an increase in its rate of formation. The stability of cytoplasmic rRNA was measured after labeling with 3H-methyl-methionine. In agreement with the results of previous studies, we found that rRNA is stable in growing cells and unstable In resting cells. Quite unexpectedly, the 16s and 28s rRNA of resting cultures were found to differ appreciably in turnover rate. In both 3T6 and 3T3, the half-life of 28s RNA is about 50 hr, and that of 185 RNA about 72 hr. For this reason, though growing ceils should synthesize the two ribosomal subunits in equal numbers, resting cells should synthesize more of the larger subunits than of the smaller. tRNA is unstable under all conditions. Its half-life is 38 hr in resting cells and about 80 hr in growing cells.
Accumulation of mature mRNA in the nuclear fraction of mammalian cells
FEBS Letters, 1999
Little is known about the nuclear mRNA content of mammalian cells. In this study, we analyzed by Northern blotting with a panel of probes the nuclear and cytoplasmic fractions derived from several rodent cell lines. For most of the genes under study, mature mRNAs could easily be detected in the nuclear fraction and accumulated to higher levels than the corresponding precursors. In addition, significant differences in the nucleocytoplasmic partition of mature mRNAs were observed between genes as well as between cell types (NIH 3T3, CTLL-2, D3-ES, PC-12), indicating that this nuclear accumulation of mRNA is regulated. Thus, while it is usually considered that splicing is the limiting step of pre-mRNA processing, these results point towards transport or nuclear retention of mRNA as a key determinant of nuclear mRNA metabolism.
Carlsberg Research Communications, 1984
The cytoplasmic accumulation of newly synthesized RNA in rat thymocytes has been analyzed during the first 45 min of protein synthesis inhibition by cycloheximide, emetin, puromycin or pactamycin. Electrophoretic fractionation of double labelled RNA showed no changes in the isotope ratio of single fractions of poly(A)'-RNA within an experimental error corresponding to +2 to +20 molecules per ceil. In poly(A)-RNA, two types of changes were induced. All four inhibitors stimulated the incorporation in presumptive histone mRNA and inhibited the accumulation of 18 S rRNA. A stimulated accumulation of tRNA was induced only by cycloheximide and emetin, two polysome stabilizing compounds. Labelling of 28 S rRNA was only slightly affected, except in the presence ofcycloheximide, where it increased more than twofold. This suggests that cycloheximide may induce an accelerated nuclear-cytoplasmic transfer of 28 S rRNA. The changes induced in poly(A)-RNA are thus either inhibitor specific, or a result of a sensitivity to protein synthesis per se.
Addition of poly(A) to nuclear RNA occurs soon after RNA synthesis
The Journal of cell biology, 1980
A kinetic analysis of the appearance of [3H]uridine label in RNA sequences that neighbor poly(A), as well as the incorporation of [3H]adenosine label into both the RNA chain and the poly(A) of poly(A)-containing molecules, shows that poly(A) is added within a minute or so after RNA chain synthesis in Chinese hamster ovary cells and HeLa cells. Previous conclusions by several groups (5-7) that poly(A) might be added as long as 20-30 min after RNA synthesis appear to be in error, and the present conclusion seems much more in line with several different types of recent studies with specific mRNAs that suggest prompt poly(A) addition (13-16).