Increase In Total RNA Research Articles

Nucleic acid metabolism during cytokinin induced cellular differentiation.

Edstrom's microphoresis technique has been employed to determine the quantitative alterations in nucleic acid content and base composition of individual cells associated with the initiation of bud primordia in Funaria hygrometrica. The filamentous protonema of this moss initiates bud cells which through repeated divisions form the leafy gametophores. The cytokinin, 6-furfurylaminopurine (kinetin), was used to induce the differentiation of bud cells from protonematal cells. The total RNA content of kinetin-induced bud cells (22.0 mumug/cell) was nearly 15 times that of protonematal cells (1.6 mumug/cell). The same dramatic increase in total RNA was apparent in bud cells which developed spontaneously in older cultures. As would be predicted, the adenine (A) to guanine (G) ratio for DNA from bud and protonematal cells was identical (0.7). The A:G ratio for RNA from bud cells (1.0) was much lower than that from protonematal cells (1.7). Thus, kinetin-induced differentiation in this system involves a dramatic increase in total RNA, the base composition of which approaches that of DNA. The base composition (A:G ratio) of DNA remains constant.

Selective synthesis of messenger RNA in a fission yeast during a step-down, and its relation to the cell cycle: Bulk experiments

Cells of the fission yeast Schizosaccharomyces pombe were transferred from a rich medium in which they grew fast to a minimal medium containing ethanol in which they grew slowly. There was no increase in optical density for 25 min after this “step-down”, and no increase in total RNA for 1 hr. RNA, however, continued to be synthesised after the step-down, as judged by the incorporation of radioactive precursors. We conclude that this RNA is largely “messenger” for the following reasons: 1. 1. It appears to be unstable, from the evidence of pulse and chase experiments with 32P and 14C-adenine. 2. 2. It has base ratios, determined from 32P labelling, which are not like ribosomal or transfer RNA and which are distorted towards DNA. 3. 3. It has sedimentation properties in sucrose gradients which are not like those of ribosomal and transfer RNA and which resemble those of messenger RNA in other systems.

Template stability in liver and hepatoma

The recent advances in the comparative biochemistry of liver tumors of different growth rates were outlined. 1. 1. The four key gluconeogenic enzymes, glucose-6-phosphatase, fructose-1,6-diphosphatase, phosphoenolpyruvate carboxykinase and pyruvate carboxylase decreased with the increasing growth rate and were absent in the rapidly-growing tumors. It was suggested that the genes for these enzymes may be localized on the same Functional Genome Unit. 2. 2. The RNA amount showed no correlation with growth rate in a spectrum of hepatomas. 3. 3. The incorporation of formate into total hepatoma RNA progressively increased with the increasing growth rate. The incorporation of orotate into RNA was markedly decreased in all tumors examined. The incorporation of formate and orotate into RNA was increased in the regenerating liver. 4. 4. Triamcinolone treatment in control, normal liver caused an increase in total RNA; however, there was no change in the hepatomas. The RNA specific activity was increased in normal liver by steroid injections and it also showed some rise in a slow-growing hepatoma. There was no response in the rapidly-growing liver tumor. 5. 5. The concentration of free amino acid did not correlate with the growth rate of hepatomas. Glucocorticoid injection caused a marked elevation in hepatic amino acid level; however, there was a complete failure of response in all hepatomas examined. 6. 6. Triamcinolone injection caused a progressive increase in hepatic glycogen, nitrogen and free amino acid content and in the activities of glucose-6-phosphatase and fructose-1,6-diphosphatase. There was a failure of response in these biochemical parameters in the kidney cortex. 7. 7. The various biochemical parameters and metabolic responses were correlated with the growth rate of hepatomas.