Induction of new proteins by gamma interferon in cultured human keratinocytes

Human epidermal keratinocytes incubated with recombinant gamma interferon (r-IFN-gamma) show, on two-dimensional gel electrophoresis, both the appearance of new proteins and the loss of others. Among [35S]methionine-labeled proteins, which are induced in an actinomycin- or alpha-amanitin-sensitive manner, is a prominent group with an apparent relative molecular mass of 53,000 and pI of 5.3-5.8. The synthesis of these proteins continues for at least 4 days in the presence of gamma interferon (IFN-gamma). Over the concentration range tested, up to 670 pM, there is no inhibition of protein synthesis, so the appearance of these proteins cannot be explained by overall inhibition of protein synthesis. Furthermore, at 4 pM we found only minor inhibition of DNA (21%) and RNA (29%) synthesis. Half-maximal induction of the prominent 53 kD proteins occurs at an interferon concentration of 0.8-3.5 pM which may be compared with a range of 1.5-30 pM for HLA-DR induction. The same prominent proteins are also induced by type I interferons. The 53 kD protein complex appears to consist of at least 4 different proteins, one of which is phosphorylated and another one of which is not induced in fibroblasts treated with IFN-gamma. We could obtain no evidence that the proteins were related by glycosylation. The presence of these proteins provides a sensitive means of identifying keratinocytes responding to interferons. Lack of these proteins in normal epidermis indicates that interferon does not play a major role in the control of keratinocyte behavior in sound skin.

Exposure to 12-O-tetradecanoylphorbol-13-acetate (TPA) induces the synthesis of histidine-rich protein (filaggrin) in monolayer cultures of rat keratinocytes

The effect of 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent tumor promoter, on epidermal differentiation has been studied by investigating the appearance of the epidermal differentiative marker protein, histidine-rich protein (HRP), in monolayer cultures of rat keratinocytes grown in low-calcium (0.1 mM) medium. Monoclonal antibody, 3F6-6, raised against the 60K HRP (HRPII) derived from the epidermis of the newborn rat was utilized to detect HRP in cultured keratinocytes. As a major component of keratohyalin in the cells of the granular layer in epidermis, HRP is not normally found in a monolayer culture of rat keratinocytes containing a high population of proliferating cells. However, when these cultures were exposed to 10 ng/ml of TPA, DNA and protein synthesis were decreased by up to 95% and 60%, respectively, and the cells in the monolayer culture became HRP-positive within 18-24 h. TPA has been shown to cause a withdrawal of the basal cells from the cell cycle and a commitment of these cells to an accelerated rate of terminal differentiation. Exposure to TPA at the same time that the calcium level of the monolayer cultures was raised to 2.0 mM in order to allow stratification resulted in positive immunostaining for HRP much earlier and much more intensively than in the absence of TPA. TPA also enhanced stratification of these cultures; however, the positive expression of HRP preceded the stratification. These observations support the view that the induction of terminal differentiation occurs independently of stratification and that the process of terminal differentiation (maturation) of basal cells precedes and triggers the movement of these cells to a suprabasal position (stratification).

Macromolecular synthesis is required for stimulation of estrogen synthetase activity by dibutyryl cyclic AMP plus theophylline in choriocarcinoma cell culture

Estrogen secretion and estrogen synthetase (aromatase) activity are stimulated in human trophoblast cells (JAr line) after addition of 1 mM dibutyryl cyclic AMP plus 1 mM theophylline (dbT) to the growth medium. The data given here show that (a) the aromatase specific activity in homogenized cells increases linearly over a 96 hr incubation period after addition of dbT; (b) addition of inhibitors of macromolecular synthesis, cycloheximide or actinomycin D, to the culture medium at the time of addition of dbT abolishes the stimulation of aromatase activity; (c) mixing dbT-grown cells, containing increased aromatase activity, with control cells does not result in an aromatase specific activity higher than the expected average, suggesting that dbT-grown cells do not contain a factor present in excess which serves to stimulate aromatase in control cells; and (d) NADPH, included in vitro in the aromatase assay or incubated with the cells for 48 hr as well as being present in the aromatase assay, has no stimulatory effect on aromatase specific activity in homogenized cells.

A temperature-sensitive mutant showing two defective functions

A temperature sensitive growth mutant, 13B11 derived from CHO-K1 has been partially characterized. Upon shift to the nonpermissive temperature (39 degrees C) DNA synthesis slows down, but it is partly resumed after prolonged incubation at 39 degrees C. The radioautographic results suggest that reduction in the rate of DNA synthesis is mainly due to decrease in the proportion of DNA synthesizing cells and that increase in that rate observed afterwards is due to appearance of cells that enter S. Synchronized mutant cells incubated at 39 degrees C from the beginning of G1 enter S with the delay of 6 hours. By incubating the cells at 39 degrees C for a restricted period during the G1 phase, some processes in late G1 are found to be susceptible to the high temperature. Mutant cells shifted up in the middle of S performed cell division whereas cells up-shifted in G1 phase did not, although about a half of these cells divided when they were shifted down in the presence of hydroxyurea. The analysis of DNA content of the cells cultured at 39 degrees C for more than one generation time, revealed the accumulation of nuclei containing DNA in amount of almost 4C level. Accordingly in this mutant the process necessary for cell division is also temperature sensitive. Considering the frequency of the appearance of spontaneous revertants (2 X 10(16)), the apparent two lesions of this mutant might be ascribed to the single mutation.

Biochemical study of minosaminomycin in relation to the kasugamycin group antibiotics

Minosaminomycin is structurally related to kasugamycin and inhibits protein synthesis in mycobacteria. It also inhibits phage f2 RNA-directed protein synthesis in a cell-free system of Escherichia coli by 50% at 2 x 10(-7) M. It is 100-times more potent than kasugamycin in this system. At 10(-7) M minosaminomycin inhibits EF-T dependent binding of aminoacyl-tRNA to ribosomes by 50%. This effect is markedly diminished if minosaminomycin is added to the assay system after a brief incubation of ribosomes with mRNA. Like kasugamycin, minosaminomycin preferentially inhibits the initiation of protein synthesis directed by phage f2 RNA in vitro and does not cause miscoding. Ribosomes from kasugamycin-resistant mutants Ksg A and Ksg C were as sensitive to minosaminomycin as those from each parent strain. In spite of the strong inhibitory activity of minosaminomycin manifested in cell-free systems of E. coli, this compound inhibits the growth of the organism itself only slightly. This discrepancy could be ascribed to impermeability, as E. coli cells with modified permeability show greater sensitivity to minosaminomycin. There is no indication that the antibiotic is activated in E. coli cells. On the basis of these results, the structural features of these antibiotics is inactivated in E. coli cells. On the basis of these results, the structural features of these antibiotics essential for interaction with ribosomes and for permeability into the cells are discussed.

Time sequence of nuclear pore formation in phytohemagglutinin-stimulated lymphocytes and in HeLa cells during the cell cycle

The time sequence of nuclear pore frequency changes was determined for phytohemagglutinin (PHA)-stimulated human lymphocytes and for HeLa S-3 cells during the cell cycle. The number of nuclear pores/nucleus was calculated from the experimentally determined values of nuclear pores/micro(2) and the nuclear surface. In the lymphocyte system the number of pores/nucleus approximately doubles during the 48 hr after PHA stimulation. The increase in pore frequency is biphasic and the first increase seems to be related to an increase in the rate of protein synthesis. The second increase in pores/nucleus appears to be correlated with the onset of DNA synthesis. In the HeLa cell system, we could also observe a biphasic change in pore formation. Nuclear pores are formed at the highest rate during the first hour after mitosis. A second increase in the rate of pore formation corresponds in time with an increase in the rate of nuclear acidic protein synthesis shortly before S phase. The total number of nuclear pores in HeLa cells doubles from approximately 2000 in G(1) to approximately 4000 at the end of the cell cycle. The doubling of the nuclear volume and the number of nuclear pores might be correlated to the doubling of DNA content. Another correspondence with the nuclear pore number in S phase is found in the number of simultaneously replicating replication sites. This number may be fortuitous but leads to the rather speculative possibility that the nuclear pore might be the site of initiation and/or replication of DNA as well as the site of nucleocytoplasmic exchange. That is, the nuclear pore complex may have multiple functions.

Nucleic acid synthesis in bacteriophage SPO2c 1 -infected Bacillus subtilis

The synthesis of host macromolecules was shut off very slowly and incompletely by bacteriophage SPO2c(1). No change in the rate of incorporation of radioactive precursors into protein and ribonucleic acid (RNA) could be detected after infection, and the rate of incorporation of thymidine was increased only slightly. The relative proportions of phage and host species of nucleic acids at various intervals in the latent period were determined by means of nucleic acid hybridization. Phage-specific RNA populations synthesized early were different from those synthesized late in the latent period. Host deoxyribonucleic acid (DNA) replication continued until 8 to 10 min after SPO2c(1) infection and then decreased markedly as phage-specific DNA synthesis was initiated. Host DNA was not degraded to trichloroacetic acid-soluble fragments, and its nucleotides were not found in either newly synthesized intracellular phage DNA or in progeny phage particles. The average burst size of SPO2c(1) was approximately 200 plaque-forming units per cell.

Osmiophilic polymer generation: catalysis by transition metal compounds in ultrastructural cytochemistry

A transition metal compound that is bound in tissues by any appropriate cytochemical reaction may catalyze the generation of an insoluble osmiophilic polymer from organic monomers such as 3,3'-diaminobenzidine. When the polymers are treated with osmium tetroxide, electron-opaque, insoluble osmium blacks (coordination polymers of osmium) are formed at the sites of the particular macromolecule or enzyme permitting its light, and electron, microscopic localization. This approach represents a distinct advantage over earlier cytochemical methods because the shorter incubation time needed here results in less artifactual deposition of metal ions, and less tendency to crystallize the reaction product. In addition, the shorter incubation times permit longer fixation of tissues and hence less artifact due to enzyme diffusion.

Morphokinetic reaction of cells of Streptococcus faecalis (ATCC 9790) to specific inhibition of macromolecular synthesis: dependence of mesosome growth on deoxyribonucleic acid synthesis

The application of quantitative electron microscopy to thin sections of cells of Streptococcus faecalis specifically inhibited for deoxyribonucleic acid (DNA), ribonucleic acid, and protein synthesis shows that septal mesosomes (i) increase in size when protein synthesis is inhibited by at least 80% while DNA synthesis proceeds at no less than 50% of the control rate and (ii) decrease in size when DNA synthesis is inhibited 50% or more during the initial 10 min of treatment. This indicates that fluctuations in mesosome size are dependent on the extent of DNA synthesis. The fluctuations in mesosome areas observed on treatment do not correlate with the kinetics of glycerol incorporation per milliliter of a culture. However, when glycerol incorporation is placed on a per cell basis, a strong correlation is observed between increases in (i) the thickness of the electron-transparent layer of the cytoplasmic membrane and (ii) the amount of glycerol incorporated per cell. It seems that the electron-transparent membrane layer may thicken to accommodate changes in lipid content when protein and lipid synthesis are uncoupled.

Morphokinetic reaction of Streptococcus faecalis (ATCC 9790) cells to the specific inhibition of macromolecular synthesis: nucleoid condensation on the inhibition of protein synthesis

In glutaraldehyde-prefixed exponential-phase cells of Streptococcus faecalis the nucleoid is "frozen" in a dispersed configuration. Exposure of exponential-phase cells to threonine starvation or to antibiotics inhibiting protein synthesis resulted in progressive condensation of nucleoid fibrils producing an expanding central nucleoid zone or pool. The condensation of the nucleoid was observed to occur at a rate directly proportional to the rate of inhibition of protein synthesis. However, the extent of nucleoid condensation depended on continuing deoxyribonucleic acid synthesis. Significantly less nucleoid condensation occurred when cells were inhibited in deoxyribonucleic acid and protein synthesis than when cells were inhibited in protein synthesis alone. These results suggest a model in which, during nucleoid replication, the chromosome fibrils are normally maintained in a dispersed state by the active agents of transcription-translation, such as ribonucleic acid polymerase molecules and ribosomes.

Biosynthesis of the wall teichoic acid in Bacillus licheniformis

1. The biosynthesis of the wall teichoic acid, poly(glycerol phosphate glucose), has been studied with a particulate membrane preparation from Bacillus licheniformis A.T.C.C. 9945. The precursor CDP-glycerol supplies glycerol phosphate residues, whereas UDP-glucose supplies only glucose to the repeating structure of the polymer. 2. Synthesis proceeds through polyprenol phosphate derivatives, and chemical studies and pulse-labelling techniques show that the first intermediate is the phosphodiester, glucose polyprenol monophosphate. CDP-glycerol donates a glycerol phosphate residue to this to give a second intermediate, (glycerol phosphate glucose phosphate) polyprenol. 3. The glucose residue in the lipid intermediates has the beta configuration, and chain extension in the synthesis of polymer occurs by transglycosylation with inversion of anomeric configuration at two stages.

The mechanism of wall synthesis in bacteria. The organization of enzymes and isoprenoid phosphates in the membrane

1. The synthesis of peptidoglycan and teichoic acids by cell-free preparations from Bacillus licheniformis A.T.C.C. 9945 and Bacillus subtilis N.C.T.C. 3610 has been studied under a variety of conditions. 2. It was shown that poly(glycerol phosphate) is synthesized through a lipid intermediate, and it is concluded from this and other work that all major bacterial wall polymers are formed in a similar manner through such intermediates. 3. Close interrelation between the synthesis of peptidoglycan and teichoic acids was demonstrated, and inhibition studies confirm that the polyprenol phosphate molecules participating in the synthesis of peptidoglycan are shared with the systems that synthesize teichoic acids. 4. Nucleotides for the synthesis of one polymer are inhibitory towards synthesis of the other, and these effects can be enhanced or diminished by preincubation of the enzyme system with appropriate nucleotide precursors. 5. It is concluded that the return of undecaprenol phosphate to a common pool occurs only after the completion of polymer chains, and not after each cycle in the attachment of individual repeating units. This and other observations support a model for bacterial wall synthesis in which the multi-enzyme systems for each polymer are closely aligned in the membrane, with a molecule of undecaprenol phosphate located between them in a manner that enables it to be shared. The general mechanisms of wall synthesis and its control are discussed.

Virus-induced interference in heterologously infected HeLa cells

In doubly infected HeLa cells, poliovirus type 1 rapidly and completely dominates vesicular stomatitis virus (VSV) plaque-forming unit production. Poliovirus type 1 shuts off incorporation of amino acids into VSV-specific proteins within 2 hr after superinfection of cells already committed to massive synthesis of VSV proteins. However, poliovirus type 1 appears to have little, if any, direct effect upon incorporation of uridine into VSV-directed ribonucleic acid (RNA) synthesis. Poliovirus apparently interferes with VSV virion production only at the level of translation of viral messenger RNA, although it interferes with host cell macromolecular syntheses at the levels of translation and transcription.

Changes in macromolecular synthesis associated with the induction of glutamine synthetase in embryonic retina

The hydrocortisone-mediated induction of glutamine synthetase in the neural retina of chicken embryo in vitro is correlated with enhanced incorporation into protein of [(14)C]aspartic acid, an amino acid abundant in this enzyme. In the induced retina labeled with [(14)C]aspartic acid, a peak of radioactivity was detected in the region of the polysomal profile corresponding to polysomes comprising 12-14 ribosomes. In retinas labeled with [(3)H]uridine, an increased amount of radioactivity was also detected in the same polysomal region of the hydrocortisone-induced retina. If we assume a monocistronic messenger RNA for retinal glutamine synthetase, this region corresponds to the estimated size of the polysomes necessary for the translation of this enzyme. The evidence presented demonstrates a correlation between these changes in incorporation and the induction of glutamine synthetase.

Nucleocytoplasmic interactions in morphogenesis

Many classical experiments have clearly established the importance of cytoplasmic organization during the very early stages of development: for instance, removal of the ‘polar lobe’ a t the trefoil stage of cleavage results, in molluscs, in various defects in the larv a ; mild centrifugation of a fertilized amphibian egg induces marked microcephaly, while inversion of its normal polarity, by keeping the egg upside down, produces Siamese twins. The dorsoventral organization of the amphibian egg can be established at will by the experimenter by simply forcing the egg to rotate in a given plane. As a result of this rotation, the dorsal side becomes visible by the appearance of the so-called grey crescent. If the cortex (about 1 jum thick) of this dorsal side is removed, the egg will cleave and form a blastula, but it will not develop further. If, on the contrary, the dorsal cortex of a fertilized egg is grafted on the ventral side of another fertilized egg, a double embryo will form (Curtis 1960). In all these experiments, nothing is apparently done to the egg nucleus, while minor alterations of the cytoplasm have farreaching consequences for further development. On the other hand, many experiments in which the nucleus has been intentionally injured (in order to produce mutations, aneuploidy, haploidy, hybridization, etc.) definitely show that nuclear integrity is required in order to obtain full and normal development. This effect of the nucleus is hardly conspicuous until the initial period of cleavage is over. But morphogenetic movements, neural induction, organogenesis, tissue and cell differentiation all require the presence of normal nuclei.