Organ-specific estrogen-induced RNA synthesis resolved by DNA-RNA hybridization in the domestic fowl

Evidence for specific DNA sequences in the nuclear acceptor sites of the avian oviduct progesterone receptor

Recent studies have shown that saturable high-capacity nuclear binding sites (termed acceptor sites) for the avian oviduct progesterone receptor can be reconstituted by rehybridizing a specific oviduct chromatin protein fraction (CP-3) to pure hen DNA to generate a reconstituted nucleoacidic protein (NAP). Only a limited number of acceptor sites can be generated on hen DNA even at high protein/DNA ratios. This suggests the existence of a limited number of specific sequences in the avian genome that can participate in the acceptor sites. The studies presented in this paper show a specificity as to the source of DNA that can generate acceptor sites using hen oviduct CP-3 protein. The acceptor protein binds to all DNAs but generates acceptor sites only on DNAs from certain animals. The acceptor sites for the progesterone receptor, generated with heterologous mammalian DNAs and the avian oviduct CP-3 fraction, show saturation not only in number of acceptor sites generated on the DNAs but also in progesterone receptor binding. Binding to these sites is also receptor dependent. Using oviduct receptors from particular physiological states of the birds wherein the receptors do not bind to nuclear sites in vivo, it was found that the cell-free binding to these heterologous complexes of hen CP-3 protein and DNA from another species, termed heterologous NAP, is similarly absent. Thus, the cell-free binding to the native oviduct NAP and the heterologous NAP markedly resembles the nuclear binding in vivo. Interestingly, synthetic DNAs rich in adenine and thymine, but not those rich in guanine and cytosine, are capable of generating acceptor sites. Species-specific DNA sequences, as well as specific chromatin proteins, therefore, appear to be involved in the nuclear acceptor sites for the avian oviduct progesterone receptor. The DNA sequences appear to be conserved throughout most of the vertebrates but not among nonvertebrates as are the steroid hormones and their receptors. The exact numbers and distributions of these sequences in the avian genome are not known.

Auxin and ribonucleic Acid synthesis in pea stem tissue as studied by deoxyribonucleic Acid-ribonucleic Acid hybridization

The ability of auxin to alter gene transcription in pea (Pisum sativum L.) stem tissues has been investigated by means of DNA/RNA hybridization-competition techniques. In order to obtain reproducible hybridization with total nucleic acid preparations from plants it was found necessary to remove interfering substances, probably polysaccharides; this was accomplished by methoxyethanol extraction and precipitation with cetyltrimethylammonium bromide. When purified in this fashion, plant nucleic acids could be made to form hybrids which showed both species specificity and high thermal stability.No change in hybridizable RNA of stem sections in response to auxin could be detected over a 2- to 24-hour period, regardless of the auxin level employed. In contrast, when large doses of auxin were applied to intact pea seedlings, definite changes in the hybridizable RNA of stem tissue were detected both 8 and 24 hours after treatment. Many of the 2,4-D-induced species of RNA which were present at 24 hours were also present at 8 hours. Sections apparently lack a factor needed for the manifestation of the auxin effect on RNA synthesis.Since the hybridization assay employed does not measure all cellular RNA, it is still possible that certain RNA species may be synthesized in sections in response to auxin. However, the auxin promotion of cell elongation in such sections is clearly not associated with changes in hybridizable RNA such as have been reported for several hormonal responses in animal systems.

The synthesis of ribonucleic acid in immature rat uterus responding to oestradiol-17 beta

Stimulation of incorporation of labelled precursors into the RNA of immature rat uterus is an early result of oestradiol-17beta action. However, the extent of the increased incorporation varies with the mode of administration of the labelled precursors and with the weight of the rat. At the age and weight range normally used response is maximal at ten times control incorporation, 4h after the administration of 0.3mug or more of oestradiol-17beta. Under these conditions the stimulation of incorporation into the acid-soluble fraction is only 2-2.5-fold. When the purified RNA is separated on polyacrylamide gels the major increase in incorporation of radioactive precursor is found in rRNA and 4S RNA; the formation of the former has been followed from the 45S precursor. Preceding these events by at least 30min, however, is an increase in the incorporation of precursor into RNA species of very high molecular weight, which remained in the first few slices of the gel. The possible significance of these findings is discussed. The increased synthesis of rRNA in response to oestradiol-17beta is more strongly inhibited by actinomycin D than the synthesis of other RNA species. Cycloheximide, depending on time of administration and dosage, inhibits either RNA synthesis or the maturation of rRNA.