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M C Schultz

Publications and source records attributed to M C Schultz.

7 recordsLinked to original sources
PubMed1992

Variants of the TATA-binding protein can distinguish subsets of RNA polymerase I, II, and III promoters.

Transcription extracts prepared from yeast that are deficient in the TATA-binding protein (TBP or TFIID) are also impaired in specific promoter recognition by all three nuclear RNA polymerases (pol I, II, and III). Specific initiation can be rescued by the addition of purified recombinant TBP, demonstrating that pol I, II, and III all require this factor. A mutation of TBP has been identified that will function with pol I but not with pol II or III. Conversely, another mutation, which inactivates TATA element binding in vitro, will function with pol I and III promoters but is inactive for a pol II promoter. Thus, it is possible to identify TBP variants that will only function on different subsets of all nuclear promoters.

DNA-Binding Proteins↗
PubMed1992

In vitro definition of the yeast RNA polymerase I promoter.

The structure of the ribosomal gene promoter from Saccharomyces cerevisiae has been analyzed in a whole cell in vitro extract. The promoter contains at least two essential domains, an upstream domain located at the 5' boundary near position -150 and a core promoter domain around the site of transcription initiation at +1. The upstream domain augments transcription in vitro but is not absolutely required. Maintenance of correct spacing between the two domains is critical. The in vitro analysis agrees well with prior in vivo analysis and it appears that the yeast promoter has a structure very similar to that of vertebrate ribosomal gene promoters.

Base Sequence↗
PubMed1992

Topoisomerases and yeast rRNA transcription: negative supercoiling stimulates initiation and topoisomerase activity is required for elongation.

Previous work has shown that rRNA synthesis is strongly inhibited in yeast top1-top2 double mutants. Here, we show that inactivation of yeast topoisomerases can have paradoxical effects on transcription by RNA polymerase I. For example, transcription of ribosomal minigenes on extrachromosomal plasmids is greatly stimulated in top1-top2 cells while accumulation of full-length endogenous rRNA is strongly inhibited. We present evidence for a mechanism that can partly account for these opposing effects on transcription. On the one hand, transcription initiation can be stimulated owing to an accumulation of negative superhelicity because polymerase I prefers to initiate on negatively supercoiled templates. Conversely, synthesis of full-length rRNA is inhibited owing to the fact that chain elongation requires a DNA relaxing activity.

Cloning, Molecular↗
PubMed1990

Three structures associated with the nucleolus in male rat germinal cells: round body, coiled body, and "nubecula" and general presence of round body at male meiosis.

In addition to chromosomes and nucleoli, three structures, i.e., round body, coiled body, and nubecula, are encountered in the nucleus during the meiotic prophase in male rats. These structures have been examined by electron microscopy in random and serial sections. The round body is a finely fibrillar, proteinaceous structure closely associated with the granular component of a nucleolus in rat spermatocytes and young spermatids. A similar structure has been observed in man, the monkey Macaca mulatta, the gastropod Achatina fulica, and the insect Locusta migratoria. Together with evidence from the literature, these results support the view that the round body is of general occurrence in the male meiocytes of eukaryotes and may, therefore, play a role in meiosis. The coiled body is a group of electron-dense elements called "coils", which average 35 nm in width, except after mid-pachytene when their size almost doubles. The coils are composed of 2-nm-wide filaments and 8 to 10-nm-wide granules, both of which are ribonucleoprotein. The coiled bodies are interpreted to be groups of "spliceosomes", that is, structures containing heterogeneous RNA and small nuclear RNA. A remarkable feature of the coiled body is its temporary disappearance at early pachytene and its reappearance at late pachytene, possibly due to drastic changes in the turnover rate of its component RNAs. The nubecula is a newly identified nuclear inclusion, composed of weakly staining threads loosely organized into a 560 nm-wide spheroid. It has been observed only in early pachytene nuclei.

Animals↗
PubMed1977

Analytic study of the Tadoma method: background and preliminary results.

Certain deaf-blind persons have been taught, through the Tadoma method of speechreading, to use vibrotactile cues from the face and neck to understand speech. This paper reports the results of preliminary tests of the speechreading ability of one adult Tadoma user. The tests were of four major types: (1) discrimination of speech stimuli; (2) recognition of words in isolation and in sentences; (3) interpretation of prosodic and syntactic features in sentences; and (4) comprehension of written (Braille) and oral speech. Words in highly contextual environments were much better perceived than were words in low-context environments. Many of the word errors involved phonemic substitutions which shared articulatory features with the target phonemes, with a higher error rate for vowels than consonants. Relative to performance on word-recognition tests, performance on some of the discrimination tests was worse than expected. Perception of sentences appeared to be mildly sensitive to rate of talking and to speaker differences. Results of the tests on perception of prosodic and syntactic features, while inconclusive, indicate that many of the features tested were not used in interpreting sentences. On an English comprehension test, a higher score was obtained for items administered in Braille than through oral presentation.

Adult↗