Induction of cellulose in Schizophyllum commune: thiocellobiose as a new inducer.

Several mono-, di, tetra-, and polysaccharides were screened for their ability to induced cellulase production by the tetrapolar hymenomycete Schizophyllum commune. Out of 21 carbohydrates screened, 4 (thiocellobiose, carboxymethylcellulose, cellobiose, and xylan) induced all three enzymes tested (carboxymethylcellulase, beta-glucosidase, and xylanase). The inducing effect increased with rising concentrations of the inducers up to a certain value, beyond which there was either a leveling off or a decrease of the enzymatic activities. The most powerful inducer, thiocellobiose, showed the highest activity at 0.5 mM. Cellobiose, carboxymethylcellulose, and xylan showed their highest activities at 1 mM and 1%, respectively. Surprisingly, sophorose did not enhance enzyme production. The enzymatic activities were monitored over a period of 24 h. Thiocelloboise elicited a response immediately after incubation, but with all other inducers there was a latency period before their effect could be measured. High-performance liquid chromatography showed no hydrolysis of thiocellobiose when incubated in the presence of S. commune extracellular enzymes.     

INCORPORATION OF TRITIATED CYTIDINE INTO RIBONUCLEIC ACID BY ISOLATED PEA NUCLEI

A new method for the isolation of the nuclei from plant tissue has been devised. This method consists in passing the plant tissue through a set of spring-loaded, counter-rotating rollers and collecting the liberated nuclei in sucrose solution containing calcium ions. A semi-automatic machine which couples the rollers with a special tissue chopping device has been constructed. It has been shown that nuclei obtained in this way actively incorporate cytidine-H³ into RNA. This incorporation is increased in the presence of nucleoside triphosphates and an energy-regenerating system.     

AML1, the target of chromosomal rearrangements in human leukemia, regulates the expression of human complement receptor type 1 (CR1) gene.

The human CR1 gene is expressed specifically in hematopoietic cells. It is suggested that some cell-type specific factors which involve in gene-specific activation or repression exist in cells according to the result that the gene expression varies differently depend on differentiation stage. Here, we demonstrate that the integrity of a polyomavirus enhancer core sequence, 5'-TGTGGT-3', is critical to the human CR1 promoter activity. AML1 is a site-specific DNA-binding protein that recognizes the enhancer core motif TGTGGT. We show that the AML1 binds specifically to this site and activates the human CR1 promoter. Furthermore, we demonstrate that the Ets binding site (GGAA) located 2 bp upstream of the AML1 site is also involved in the regulation of the human CR1 promoter activity. Point mutations of either the AML1 or the Ets binding site that abolish the binding of the respective factors result in significant decreases of the human CR1 promoter activity. These results suggest that AML1 and Ets proteins direct the expression of the human CR1 promoter.