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L Millstein

Publications and source records attributed to L Millstein.

7 recordsLinked to original sources
PubMed1989

Two TFIIIA activities regulate expression of the Xenopus 5S RNA gene families.

Immunoblotting experiments with polyclonal and monoclonal anti-transcription factor IIIA (TFIIIA) antibodies reveal different electrophoretic forms of TFIIIA in extracts from immature and mature oocytes of Xenopus laevis. The well-characterized 39-kD TFIIIA species is present in approximately 10(12) copies per cell in stage I-III previtellogenic oocytes and declines in abundance by 10- to 20-fold during oogenesis. An immunologically related protein of apparent molecular mass of 42 kD is present at 2-4% of the level of 39-kD TFIIIA in immature oocytes, and the level of this protein increases dramatically during oogenesis. Both the 39- and 42-kD proteins are complexed with 5S RNA in 7S ribonucleoprotein (RNP) particles. High-level transcription of the oocyte-type 5S genes in vitro requires 39-kD immature oocyte TFIIIA, whereas both 39-kD TFIIIA and the mature oocyte TFIIIA species of 42 kD support somatic-type 5S transcription. TFIIIA of 42 kD does not support oocyte-type 5S transcription in a fractionated transcription system derived from mature oocytes. Both proteins, however, bind the oocyte-type and somatic-type genes with comparable affinities and exhibit similar DNase footprints on both genes. These results suggest a model for the developmental regulation of 5S RNA gene transcription where 42-kD TFIIIA serves as an activator of somatic-type 5S transcription and as a repressor of oocyte-type transcription during early embryogenesis.

Animals↗
PubMed1987

Differential transcription of Xenopus oocyte and somatic-type 5 S genes in a Xenopus oocyte extract.

We have measured the transcription of Xenopus laevis oocyte and somatic-type 5 S RNA genes in S-150 extracts prepared from ovaries of mature X. laevis females (Glikin, G. C., Ruberti, I., and Worcel, A. (1984) Cell 37, 33-41). We find that somatic-type 5 S genes are transcribed at least 40-fold more efficiently than oocyte-type 5 S genes. Since adenovirus VA, Xenopus OAX, and Xenopus tRNAMet genes are all transcribed at levels similar to that of the somatic-type 5 S gene, this difference reflects a low level of oocyte-type 5 S gene transcription. Somatic-type 5 S transcription is a linear function of somatic-type 5 S DNA concentration and this, together with the efficient transcription of other class III genes, suggests that RNA polymerase III and the general class III transcription factors are not limiting under the conditions used here. Moreover, the 5 S gene-specific transcription factor TFIIIA does not limit transcription under these conditions as preincubation with purified TFIIIA does not alter transcription of either gene, and both genes exhibit characteristic TFIIIA footprints under transcription conditions in the S-150. Somatic-type 5 S DNA incubated in the S-150 and then injected into oocyte nuclei is actively transcribed whereas oocyte-type 5 S DNA treated in the same manner is inactive. We conclude that factors in the S-150 distinguish between somatic and oocyte-type 5 S genes, assembling active complexes preferentially on the former and inactive complexes preferentially on the latter. This process is not explained by binding properties of transcription factors for these genes as currently understood and represents a previously unrecognized mechanism of transcriptional regulation of the Xenopus 5 S genes.

Animals↗
PubMed1987

Transcriptionally inactive oocyte-type 5S RNA genes of Xenopus laevis are complexed with TFIIIA in vitro.

An extract from whole oocytes of Xenopus laevis was shown to transcribe somatic-type 5S RNA genes approximately 100-fold more efficiently than oocyte-type 5S RNA genes. This preference was at least 10-fold greater than the preference seen upon microinjection of 5S RNA genes into oocyte nuclei or upon in vitro transcription in an oocyte nuclear extract. The approximately 100-fold transcriptional bias in favor of the somatic-type 5S RNA genes observed in vitro in the whole oocyte extract was similar to the transcriptional bias observed in developing Xenopus embryos. We also showed that in the whole oocyte extract, a promoter-binding protein required for 5S RNA gene transcription, TFIIIA, was bound both to the actively transcribed somatic-type 5S RNA gene and to the largely inactive oocyte-type 5S RNA genes. These findings suggest that the mechanism for the differential expression of 5S RNA genes during Xenopus development does not involve differential binding of TFIIIA to 5S RNA genes.

Animals↗
PubMed1986

Consumer attitudes about advertisements for medicinal drugs.

Approximately 1500 subjects were exposed to magazine or television advertisements for fictitious prescription drug products. The ads varied the way risk information was incorporated into the ad. Ads presented in the magazine, ads that contained detailed and specific descriptions of the drug's risks, and ads that used communications devices to emphasize risks (graphic subtitles or a separate announcer to read the risk material) were negatively evaluated. Television ads were more likely to lead subjects to state that they would consult a doctor about the medicine but not to be upset if the doctor refused to prescribe it. Evidently, television produced more positive but more tentative impressions about the product compared to the magazine. General risks informing people about the importance of the doctor in making prescribing decisions appeared to be reassuring. Older subjects had more positive views of the drug and the ad, were more receptive to the doctor's advice and were more concerned about the disease. The elderly may have viewed drugs as a symbol of health, whereas, younger subjects may have viewed them as a symbol of illness.

Adult↗
PubMed1984

Competition between Xenopus satellite I sequences and Pol III genes for stable transcription complex formation.

We have constructed hybrid plasmids bearing both Xenopus 5S RNA genes and satellite I sequences in order to test the effect of satellite DNA on 5S gene transcription. Satellite sequences inactivate 5S transcription in both HeLa S100 and Xenopus oocyte microinjection transcription assays. Inactivation of 5S transcription by satellite DNA is observed both in cis and in trans. Transcription of a tRNA gene is also precluded by satellite I DNA. The Xenopus satellite I repeat contains an RNA polymerase III transcription unit which is highly active in both assay systems. This promoter element is 10- to 25-fold more efficient than the 5S gene in transcription competition assays. This quantitative difference in affinity for transcription components may explain the inactivation of 5S transcription by satellite sequences. The satellite I promoter forms stable transcription complexes in vitro which do not dissociate for at least 30 rounds of transcription. Although stable complex formation on the satellite promoter is largely temperature independent over the range of 0-20 degrees, complex formation on both 5S and tRNA genes exhibits a steep temperature dependence characteristic of DNA helix unwinding. The DNA sequence requirements for stable complex formation on 5S genes have been determined using 5' deletion mutants.

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PubMed1984

Eukaryotic transcription complexes.

Accurate transcription of eukaryotic genes in vitro is preceeded by the assembly of the template DNA into stable DNA-protein complexes. Such complexes have been reported for genes transcribed by each of the three eukaryotic RNA polymerases. DNAase I protection or footprint assays have yielded information as to the sites of protein factor binding. These sites correlate with many of the sequences which have been implicated as promoter elements through analysis of deletion mutants. Stable transcription complexes are also formed in microinjected Xenopus oocytes and such complexes can be shown to exist in vivo in nuclei and chromatin. The propagation of active transcription complexes may prove to be a crucial element in cellular differentiation.

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