The activity of the mouse ribosomal promoter was examined after fusion to the gene coding for chloramphenicol acetyltransferase (CAT) and transfection into mouse cells. Very little CAT enzyme but high levels of CAT-specific RNA correctly initiated at the ribosomal DNA start site were synthesized. The amount of specific transcripts was neither influenced by long stretches of upstream spacer sequ...

Addition of serum, containing fibroblast growth factors, to a culture of resting 3T6 cells stimulates a transition to the growing state. Studies of ghost monolayers prepared with the aid of detergent at intervals after stimulation showed an increase in the rate of ribosomal RNA synthesis within 10 min. The rate continued to increase for many hours and reached a level 2.5- to 3.5-fold higher by ...

Despite the fact that ribosomal ribonucleic acid constitutes the bulk (85%) of cellular RNA, its mode of origin is little understood. While clearly not exhaustive , two alternatives can, at present, be entertained. One, would assume a DNA-dependent r e a ~ t i o n l-~ and the other would invoke a synthetic mechanism independent of DNA. The fact that the base composition of ribosomal RNA shows n...

SANDLER (1970) suggested that mutation, abnormal oocyte (abo:2-38), may influence the function of the ribosomal RNA cistrons. We have examined the abo mutation and its interaction with the ribosomal D N A of Drosophila melanogaster. We observed that the expression of the abo phenotype is unstable under the appropriate conditions, a behavior which paralleled changes in the phenotypic expression ...

Previously, we found that gene expressions for ribosomal RNA differ in tumorous and normal cells, so we compared the distributions of ribosomal cistrons in subfractions of nuclei from Ehrlich ascites tumor and mouse liver cells. The mean number of nucleoli per nucleus is mouse liver (diploid cells) is 3.7 while, in hyperdiploid and hypotetraploid strains of Ehrlich ascites tumors, the means are...

Centromeres, telomeres, and ribosomal gene clusters consist of repetitive DNA sequences. To assess their contributions to the spatial organization of the interphase genome, their interactions with the nucleoskeleton were examined in quiescent and activated human lymphocytes. The nucleoskeletons were prepared using "physiological" conditions. The resulting structures were probed for specific DNA...

The activity of ribosomal gene clusters has been studied by cytological methods in human cultured cells grown in different amounts of serum under controlled experimental conditions. It has been shown that increasing amounts of serum induce an increase in ribosomal RNA synthesis at the single cell level. Furthermore, the concomitant identification of individual rRNA gene clusters by fluorescent ...

Evolutionary divergence among species of the yeast genus Saccharomyces was estimated from measurements of deoxyribonucleic acid (DNA)/DNA and ribosomal ribonucleic acid (RNA)/DNA homology. Much diversity was found in the DNA base sequences with several species showing little or no homology to the three reference species, S. cerevisiae, S. lactis, and S. fragilis. These three reference species a...

The ribosomal protein L41 gene of Phaffia rhodozyma was cloned and used as a dominant selectable marker for cycloheximide resistance in the transformation of P. rhodozyma. Electrotransformation with a plasmid containing a ribosomal DNA fragment as a targeting signal typically yielded 800 to 1,200 transformants/microgram of DNA with an integrated copy number of about seven per haploid genome.

Wheat and barley DNA enriched for ribosomal RNA genes was isolated from actinomycin D-CsCl gradients and used to clone the ribosomal repeating units in the plasmid pAC184. All five chimeric plasmids isolated which contained wheat rDNA and eleven of the thirteen which had barley rDNA were stable and included full length ribosomal repeating units. Physical maps of all length variants cloned have ...