Characterization of messenger RNA in protoplasts of Saccharomyces carlsbergensis

Isolation and characterization of an actinomycin D-sensitive mutant of Saccharomyces cerevisiae

A single mutation in Saccharomyces cerevisiae conferred sensitivity to low concentrations of actinomycin D. Treatment with actinomycin D preferentially inhibited synthesis of rRNA's. Residual rRNA synthesized was processed normally. Total protein synthesis and inducibility of the enzyme maltase were relatively unaffected at concentrations of actinomycin D which severely inhibited rRNA synthesis.

An improved procedure of specific polysome precipitation with antibody

The specific immunoprecipitation of polysomes prepared from a mouse myeloma, 31C, synthesizing an IgG1 immunoglobulin has been investigated. A reported method in which polysomes were coprecipitated by sequential addition of antibody to 31C myeloma protein, antigen (i.e., the 31C protein) and again the antibody, was used. Salt concentration greatly affected the immunoprecipitation of polysomes. In the presence of 100 mM KCl or NaCl, 10-20% of myeloma polysomes and only 1% of mouse liver polysomes were precipitated with the antibody to myeloma protein. On the other hand, 90% of the both polysomes were precipitated by the same antibody at a salt concentration of 10 mM. Triton X-100 and sucrose had little effect on preventing nonspecific binding of immunoglobulin to ribosomes. Experiments were carried out to obtain an optimal ratio of the amount of polysome to that of antibody and antigen to be added for the coprecipitation of polysomes. To date we have tried 25 mug of the first antibody, 14 mug of antigen added second to the polysomes and 38 mug of the antibody added finally and these were found to precipitate most efficiently one A260 unit of 31C polysomes.

Characterization of messenger-like ribonucleic acid from Saccharomyces cerevisiae by the use of chromatography on methylated albumin-kieselguhr

Chromatography on methylated albumin-kieselguhr of RNA from Saccharomyces cerevisiae was used to separate stable RNA from a tenaciously bound DNA-like RNA fraction. The tenaciously bound RNA, which was eluted with a dilute solution of sodium dodecyl sulphate, was characterized as messenger-like RNA by its sedimentation behaviour, nucleotide composition, lack of methylated bases and labelling kinetics. Chromatography of purified ribosomal RNA indicated a minor contamination of the tenaciously bound fraction with ribosomal RNA. On the other hand, a large portion of pulse-labelled polyribosomal RNA from protoplasts of Saccharomyces cerevisiae was tenaciously bound to the columns. The ;chase' of isotopic label from the messenger-like RNA was found to be retarded during inhibition of protein synthesis both by cycloheximide and by starvation for a carbon source.