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Analysis of isoaccepting transfer ribonucleic acid species of Bacillus subtilis: chromatographic differences between transfer ribonucleic acids from spores and cells in exponential growth.

Differences between the transfer ribonucleic acid (tRNA) of spores and exponentially growing cells of Bacillus subtilis 168 were compared by co-chromatography on reversed-phase column RPC-5. This system gave excellent resolution of isoaccepting species in 1 to 2 hr using a 200-ml gradient. Two methods were used to extract spore tRNAs, a procedure using a Braun homogenizer and a pretreatment with dithiothreitol followed by lysis with lysozyme. Where changes were observed, column elution profiles of spore tRNAs were independent of the extraction method used. Three kinds of changes between the profiles of vegetative cell tRNA and spore tRNA were observed: (i) no change; phe-, val-, ala-, asp-, ileu-, pro-, met-, fmet-, and his-tRNAs, (ii) a change in the ratio of existing peaks; gly-, tyr-, leu-, ser-, thr-, aspn-, and arg-tRNAs, and (iii) the appearance or disappearance of unique peaks; lys-, glu-, and trp-tRNAs.

Acylation↗

Enzymatic and chemical structure mapping of mouse 28S ribosomal ribonucleic acid contacts in 5.8S ribosomal ribonucleic acid.

Secondary structure mapping experiments using S1 nuclease, RNase T1, and diethyl pyrocarbonate as conformational probes have identified those regions in mouse 5.8S rRNA containing major sites of interaction with 28S rRNA. One site encompasses the 3'-terminal 20 nucleotides and corresponds to the region identified previously as a component of an RNase-resistant 5.8S/28S rRNA junction complex. A second site, located at the 5' terminus, has not been defined precisely but is believed to involve approximately 20--30 nucleotides. The existence of these sites of interaction is supported by comparing sequences of eukaryotic 5.8S and 28S rRNA with those of the prokaryotic 23S rRNA. Evidence for the occurrence of at least three helical regions in the central portion of the mouse 5.8S rRNA molecule is also presented.

Animals↗

Changes in the synthesis of ribosomal ribonucleic acid and of poly(A)-containing ribonucleic acid during the differentiation of intestinal epithelial cells in the rat and in the chick.

Epithelial cells were isolated from rat and chick small intestine by techniques which separated subpopulations of differentiating villus and upper crypt cells from each other and from populations of mitotically dividing lower crypt cells. Incorporation of precursors into epithelial-cell DNA, cytoplasmic rRNA and cytoplasmic poly(A)-containing RNA occurred in the lower crypt cells in vivo when precursor was supplied from the vascular system of the intestine. Incorporation of precursor into 28S and 18S rRNA continued in the upper crypt cells, but occurred to only a very slight extent (if at all) in villus cells, whereas incorporation into poly(A)-containing RNA continued (at a diminishing rate) as the differentiating cells migrated along the villi. When precursor was supplied from the intestinal lumen, its incorporation into DNA and into rRNA of crypt cells was not very different from that observed with the other mode of precursor administration, but incorporation into villus-cell poly(A)-containing RNA then occurred at essentially the same rate in all intestinal epithelial cells in vivo. Cytoplasmic poly(A)-containing RNA appeared to turn over in rat crypt cells with a half-life not exceeding 24 h; crypt-cell rRNA showed no turnover and no evidence could be found for the presence of 'metabolic DNA'.

Animals↗