caa a22 4500 465758754 CHVBK 20180323111854.0 cr unu---uuuuu 170327e19900501xx s 000 0 eng 10.1007/BF00334516 doi (NATIONALLICENCE)springer-10.1007/BF00334516 The genetics of RNA polymerases in yeasts [Elektronische Daten] [Christine Mosrin, Pierre Thuriaux] Conclusion and perspectives: Over the past few years, substantial progress has been made in the genetic characterization of yeast RNA polymerases. Most of their genes have been identified and their complete cloning and sequencing is within reach. Several conclusions can be drawn at this stage. First, the two large subunits are remarkably conserved in all cellular organisms, and are thus likely to define a "minimal” RNA polymerase carrying out the main catalytic aspects of the polymerizing reaction. Highly conserved domains have been identified and are being analyzed using conditional mutants. Second, with the exception of B32, the small subunits tested so far are essential for cellular growth and are directly involved in the transcription process as judged from the inhibition of transcription by corresponding antibodies, and from the properties of the conditional or leaky mutants so far available. They are thus genuine components of the transcription machinery even if their precise functions remain to be identified. Their amino acid sequences are unrelated to those of bacterial proteins involved in transcription. Finally, genetic and biochemical data concur in showing that certain subunits, such as B32, are "dispensable” and thus fulfill an accessory role in transcription. In spite of these advances, we are still far from being able to translate our knowledge of the primary sequence of the various subunits into functional terms: conditional or leaky mutants have been obtained for several subunits, but their biochemical characterization has been slow, and most appear to be defective in the accumulation of the protein rather than in its catalytic activity. Moreover, the spatial organization of eukaryotic RNA polymerases remains largely unknown, although a first electron microscopy characterization of enzyme A has been obtained at 2.5 nm resolution (Schultz et al. in preparation). The study of intragenic, or extragenic, suppressors of conditional, or even non-conditional, mutants may guide structural studies by defining sites that directly interact within or between distinct subunits (Nonet and Young 1989). Extragenic suppressors may also identify other components of the transcription machinery such as the enzyme-specific transcription factors, which are meanwhile being analyzed by direct cloning procedures (Eisenmann et al. 1989; Hahn et al. 1989; Horikoshi et al. 1989; Schmidt et al. 1989; Cavallini et al. 1989). finally, we still do not know if, and how, the synthesis of the three RNA polymerases is coordinatedly or differentially regulated in response to changes in the overall cellular growth rate. Springer-Verlag, 1990 Mosrin Christine Service de Biochimie, Départment de Biologie, Centre d'Etudes Nucléaires de Saclay, F-91191, Gif sur Yvette Cedex, France aut Thuriaux Pierre Service de Biochimie, Départment de Biologie, Centre d'Etudes Nucléaires de Saclay, F-91191, Gif sur Yvette Cedex, France aut Current Genetics Springer-Verlag 17/5(1990-05-01), 367-373 0172-8083 17:5<367 1990 17 294 https://doi.org/10.1007/BF00334516 text/html Onlinezugriff via DOI 1 review-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00334516 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Mosrin Christine Service de Biochimie, Départment de Biologie, Centre d'Etudes Nucléaires de Saclay, F-91191, Gif sur Yvette Cedex, France aut NATIONALLICENCE 700 1- Thuriaux Pierre Service de Biochimie, Départment de Biologie, Centre d'Etudes Nucléaires de Saclay, F-91191, Gif sur Yvette Cedex, France aut NATIONALLICENCE 773 0- Current Genetics Springer-Verlag 17/5(1990-05-01), 367-373 0172-8083 17:5<367 1990 17 294 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer