Effects of estrogen on gene expression in chick oviduct. The role of chromatin proteins in regulating transcription of the ovalbumin gene

Differential inhibition of transcription of DNA by melanoma chromosomal proteins

Histones and 4 nuclear nonhistone protein fractions (NHP1-4) were extracted from nuclei of a Cloudman mouse melanoma cell line (NCTC 3960, CCL 53) and tested for their ability to bind to DNA and influence transcription. The histones and NHP fractions showed different binding affinities for DNA, with the histones and NHP1 exhibiting the highest affinity. The NHP fractions differentially affected both the rate of RNA synthesis and the size of RNA transcribed. NHP1 which inhibited RNA synthesis to the greatest extent, inhibited synthesis of all sizes of RNA except for major peaks of 28S and 8S RNS and discrete minor peaks of 7S, 6S, 5S, and 4S RNS. Histones markedly enhanced the effect of NHP1 on RNA synthesis. These results suggest that there are nonhistone proteins in Cloudman melanoma nuclei which have a high affinity for DNA and which may be involved in the regulation of transcription.

DNA-dependent RNA polymerases from bovine thyroid: catalytic properties and template specificities

1. DNA-dependent RNA polymerases I and II have been purified starting from bovine thyroid nuclei yielding a purification factor of 230 for the RNA polymerase I and a purification factor 3212 for RNA polymerase II. RNA polymerase II was further characterized by gel electrophoresis and amino-acid analysis. 2. Kinetics and optimal assay conditions for both RNA polymerases were studied. 3. The template efficiency of a number of DNA preparations was investigated. 4. Rifamycin AF 013 and heparin act as initiation inhibitors. 5. Polyamines were shown to enhance the rate of chain elongation.

Enrichment of selected active human gene sequences in the placental deoxyribonucleic acid fraction associated with tightly bound nonhistone chromosomal proteins

A DNA fraction which is highly enriched in active gene sequences and tightly associated with a subset of nonhistone chromosomal proteins has been isolated from human placenta. After extraction with 2 M NaCl, placental chromatin was separated into two distinct components by centrifugation. Of the total DNA, approximately 96% (DNA-S) is protein free, while the remaining 4% (DNA-P) is tightly complexed with nonhistone chromosomal proteins. Reassociation studies revealed that the DNA-P fraction was enriched 22-fold in actively transcribed human placental lactogen gene sequences, while the DNA-S fraction was correspondingly depleted 22-fold in these sequences. Approximately 45% of the sequences present in DNA-P (equivalent to 1.8% of the genome) were not present in the DNA-S fraction. Reassociation of nick-translated DNA-P to DNA from a partial digest of DNase I treated nuclei indicated that 27% of the DNA-P sequences were DNAase I sensitive, suggesting they may represent actively transcribed gene sequences. Analysis of the overall sequence organization of DNA-P showed that relative to unfractionated DNA and DNA-S, DNA-P was enriched in single-copy sequences, slightly enriched in the class of middle repetitive sequences from C0t 0.01 to 100 M.s, devoid of the more highly repetitive sequences (C0t less than or equal to 0.01). The distribution of total active placental genes between DNA-P and DNA-S was measured by hybridization with a complementary DNA probe transcribed from total polysomal poly(A+) messenger RNA. We found that 57% of this cDNA probe reassociated to DNA-P and 58% to DNA-S, while 95% reassociated to DNA-P mixed with DNA-S at the observed ratio of 4 to 96, suggesting that the DNA-P fraction contained a different population of active gene sequences than DNA-S. From these results we estimate that approximately 85% of the transcribed sequences appear to be distinctly distributed and equally proportioned between DNA-P and DNA-S, while approximately 15% of the transcribed sequences are common to both fractions. We suggest that the strong affinity of the tightly bound nonhistone chromosomal proteins for the DNA-P fraction indicates a likely role for these proteins in the regulation of gene expression.

Early effect of estrogen on chromatin ultrastructure in endometrial nuclei

The effect of estradiol on chromatin ultrastructure in interphase nuclei was studied in immature rat and lamb endometrium. Physiological doses of estradiol within the first hour transformed the condensed chromatin into dispersed chromatin both in vivo and in vitro. These ultrastructural modifications were specifically induced by hormones translocating the estrogen receptor to the nucleus of estrogen-responsive tissues. Conversely, the antiestrogen tamoxifen gave a hypercondensation of chromatin. The addition of actinomycin D, cordycepin or alpha-amanitin, but not of cycloheximide, prevented the effect of estradiol both on the ultrastructural change and on [3H]uridine incorporation, suggesting that chromatin decondensation was closely related to transcriptional activity. These results indicate that in endometrium, estrogen rapidly provokes a large and extended modification of chromatin ultrastructure, which suggest a general effect on chromatin function rather than a selective activation of a limited number of genes.

Electrophoretic profiles of nonhistone nuclear proteins of human hearts with muscular subaortic stenosis

Muscular subaortic stenosis (MSS) is a genetically determined cardiomyopathy, whereas right ventricular infundibular hypertrophy (IH) apparently is an acquired condition. Since genetic expression in eukaryotic cells may be regulated primarily by DNA-associated proteins, we isolated and characterized the proteins of heart nuclei from nine patients with MSS, eight with IH, and two with normal (N) hearts. More than 150 proteins could be identified by two-dimensional polyacrylamide gel electrophoresis. Proteins in the entire region from pH 7.0 to 9.0 with molecular weights (Mr) ranging from 35,000 to 41,000 and a protein focusing from pH 5.2 to 5.3 with Mr of 55,000 were strikingly reduced in MSS. Again the electrophoretic patterns of N and IH were similar. The electrophoretic patterns of nonhistone nuclear protein (NHNP) in MSS relative to N showed a striking resemblance to those demonstrated previously for the early stage (myolytic phase) of hamster cardiomyopathy relative to the matched control. Since NHNP interacting with DNA appears to play a major role in genetic expression, it is possible that some of the manifestations of MSS could be due to different components of NHNP in the affected hearts.

Studies on the degradation of HeLa non-histone proteins

The hydrolysis of HeLa non-histone nuclear proteins over 24 h has been monitored in dilute alkali at 4, 15 and 25 degrees C using the standard ninhydrin estimation, dansylation and various electrophoresis techniques. Under conditions (up to 0.2 N NaOH, 4 degrees C) that do not release a significant quantity of ninhydrin-positive material or new N-terminal end group considerable breakdown was observed by two-dimensional electrophoresis analysis. The number of stained spots decreased from approx. 140 to 25--30. No internal protease activity could be found. Labelling studies (14C-labelled amino acids) showed that much of the hydrolysed material was extracted from the gel during normal staining and destaining procedures. Peptides could be extracted from alkali-hydrolysed non-histone protein with acid/ethanol and could be further separated by thin-layer chromatography on silica gel G. Short-term labelling of HeLa cells (14C-labelled amino acids for up to 60 min) revealed that these peptides probably have a high rate of turnover. [14C]Glucosamine studies also indicated the presence of considerable carbohydrate material in the low molecular weight products of this alkaline hydrolysis. Various standard proteins and histones were unaffected by hydrolysis in up to 0.2 N NaOH (4 degrees C, 24 h) as judged by gel electrophoresis. Seven different phosphate-splitting enzymes and an esterase had no effect on the non-histone protein electrophoresis patterns but a preparation of phospholipase C which had no protease activity towards eight standard proteins did produce considerable breakdown in HeLa non-histone proteins similar to that produced by 0.2 N NaOH at 4 degrees C.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins. V. The steroids

Since the induction of neoplastic cells by steroids has been well documented, an attempt is made to formulate a mechanism for explaining the resultant embryonic features of such tumour cells. Special emphasis is given to estrogen receptor complexes and their effect on chromatin proteins. Specifically a mechanism is presented for estradiol-17-beta and its ability to alter the gene expression (derepression) of mammary gland epithelial cells. In this model we explore the possible effects of small differences in receptor or repressor proteins associated with estrogens to translate quantitative steroid administration into qualitative cellular responses.

[Regulatory proteins in chromatin of eucaryotes]

Experimental evidence for a role of histones and chromosomal nonhistone proteins in the regulation of transcription in eucaryots is described. A speculative model on the regulation of gene activity in higher organisms is presented.

Factors influencing association of glucocorticoid receptor-steroid complexes with nuclei, chromatin, and DNA: interpretation of binding data

Attempts to reconstruct, in a test tube, the steroid-hormone system of a responsive cell are fraught with enumerable difficulties. In this chapter I have attempted to point out some of the factors that affect receptor-steroid complexes and their interactions with acceptors. In most cases there is a quantitative influence of these factors on the level of steroid complex binding to acceptors. In some cases, selected experimental designs that neglect these factors and methods of presenting the observed data may lead to artifactual conclusions. Several of these problems should disappear when the prospect of pure receptor-steroid complexes [127, 147, 150, 181, 247, 248] becomes a common occurrence. Nevertheless much has already been learned about the interactions of complexes with acceptors, which in turn have been used to help formulate models of steroid-hormone action.

Comparison of transcription stimulating, phenol-soluble non-histone chromosomal proteins in normal rat liver and transplantable hepatocellular carcinomas

The non-histone chromosomal proteins (NHCP) of a rapidly and slowly proliferating transplantable hepatocellular carcinoma (THC) were compared to those of normal and regenerating rat liver. The total quantity of NHCP is approximately threefold higher in the THCs than in either normal rat liver at 4 h and 44 h regenerating rat liver. Only those NHCP that can be extracted from chromatin by 0.35 M NaCl were further examined and it was observed that the proteins of this highly complex fraction could be further fractionated by their differential phenol-solubility. The phenol-soluble 0.35 NHCP contained protein(s) capable of stimulating the level of DNA-directed RNA synthesis in vitro. The total amount of this stimulatory activity was 5 times higher in the rapidly growing THC and 1.6 times higher in the slowly growing THC than in normal rat liver. In order to assess the contribution of cell-cycle dependent alterations on the increase in the amount of stimulatory activity in the THCs, 44 h regenerating rat livers were examined. This tissue represents a mix of cells in various stages of the cell cycle which is similar to that found in the THCs. It was found that the total quantity of NHCP in the 44 h regenerating rat liver was the same as in normal rat liver. The total amount of the stimulatory activity also was similar in both the normal and 44 h regenerating rat liver. The amount of the stimulatory activity was found to double in 4 h regenerating rat liver, however. These data suggest that the alterations observed in the NHCP of the THCs are not due solely to cell cycle dependent changes, but may represent malignancy dependent alterations.