Showing papers by "Herman M. Kalckar published in 1987"

Oligonucleotides with rapid turnover of the phosphate groups occur endogenously in eukaryotic cells.

Abstract: Endogenous oligonucleotides were found in trichloroacetic acid extracts of hamster lung fibroblasts and Tetrahymena cells. Peaks of radioactivity that eluted with retention times similar to oligonucleotide markers (5- to 50-mer) were found by HPLC in cells labeled briefly with 32Pi. Only minute amounts of UV-absorbing material were detected, consistent with a rapid turnover of phosphate groups. The 32P-labeled material also migrated as oligonucleotides on 20% polyacrylamide gels; it was not hydrolyzed by alkaline phosphatase but was digested by snake venom phosphodiesterase, S1 nuclease, and pancreatic RNase and was phosphorylated by T4 polynucleotide kinase. The 32P-labeled material isolated by HPLC was alkali labile and the hydrolyzate ran as nucleotides on paper chromatography. It is concluded that the oligonucleotides are mainly oligoribonucleotides, but it is possible that oligodeoxynucleotides are also present.

Tunicamycin tightens the glucose- and D-allose-mediated control of hexose transport in a metabolic fibroblast mutant.

Abstract: The hexose transport system of a fibroblast mutant, DS7, unable to convert glucose 6-phosphate to fructose 6-phosphate ("the phosphoglucose isomerase mutant"), is subject to a specific down-regulation ("curb") evoked by only glucose or D-allose. Neither fructose nor mannose has a curbing effect on this mutant. Further addition of tunicamycin intensified the transport curb on the mutant mediated by glucose or allose. Mannose added to the parental cell line 023 seems able to mimic a glucose-mediated transport curb. In this line, but not the mutant, tunicamycin also intensifies a mannose-mediated curb. It seems that the tightening of the allose-mediated curb is a function of a specific type of transport regulation and perhaps too of interference with glycosylation of the hexose transporter. Furthermore, this type of curb can be strikingly reversed by shifting the cultures to medium containing fructose.