Topic
Specificity factor
About: Specificity factor is a research topic. Over the lifetime, 1098 publications have been published within this topic receiving 59867 citations.
Papers published on a yearly basis
Papers
TL;DR: The crystal structure of a bacterial RNA polymerase holoenzyme from Thermus thermophilus at 2.6 Å resolution provides insight into the structural organization of transcription intermediate complexes and into the mechanism of transcription initiation.
Abstract: In bacteria, the binding of a single protein, the initiation factor sigma, to a multi-subunit RNA polymerase core enzyme results in the formation of a holoenzyme, the active form of RNA polymerase essential for transcription initiation. Here we report the crystal structure of a bacterial RNA polymerase holoenzyme from Thermus thermophilus at 2.6 A resolution. In the structure, two amino-terminal domains of the sigma subunit form a V-shaped structure near the opening of the upstream DNA-binding channel of the active site cleft. The carboxy-terminal domain of sigma is near the outlet of the RNA-exit channel, about 57 A from the N-terminal domains. The extended linker domain forms a hairpin protruding into the active site cleft, then stretching through the RNA-exit channel to connect the N- and C-terminal domains. The holoenzyme structure provides insight into the structural organization of transcription intermediate complexes and into the mechanism of transcription initiation.
801 citations
TL;DR: The devices used to control s Sigma factor activity in B, subtilis may prove to be as widespread as multiple sigma factors themselves, providing ways of coupling sigma factor activation to environmental or physiological signals that cannot be readily joined to other regulatory mechanisms.
604 citations
TL;DR: It is demonstrated here that rpoS/sigma S expression is not only transcriptionally controlled, but is also extensively regulated at the levels of translation and protein stability, and sigma S is a highly unstable protein in exponentially growing cells, that is stabilized at the onset of starvation.
Abstract: The second vegetative sigma factor sigma S (encoded by the rpoS gene) is the master regulator in a complex regulatory network that governs the expression of many stationary phase-induced and osmotically regulated genes in Escherichia coli. Using a combination of gene-fusion technology and quantitative immunoblot, pulse-labeling, and immunoprecipitation analyses, we demonstrate here that rpoS/sigma S expression is not only transcriptionally controlled, but is also extensively regulated at the levels of translation and protein stability. rpoS transcription is inversely correlated with growth rate and is negatively controlled by cAMP-CRP. In complex medium rpoS transcription is stimulated during entry into stationary phase, whereas in minimal media, it is not significantly induced. rpoS translation is stimulated during transition into stationary phase as well as by an increase in medium osmolarity. A model involving mRNA secondary structure is suggested for this novel type of post-transcriptional growth phase-dependent and osmotic regulation. Furthermore, sigma S is a highly unstable protein in exponentially growing cells (with a half-life of 1.4 min), that is stabilized at the onset of starvation. When cells are grown in minimal glucose medium, translational induction and sigma S stabilization occur in a temporal order with the former being stimulated already in late exponential phase and the latter taking place at the onset of starvation. Although sigma S does not control its own transcription, it is apparently indirectly involved in a negative feedback control that operates on the post-transcriptional level. Our analysis also indicates that at least five different signals [cAMP, a growth rate-related signal (ppGpp?), a cell density signal, an osmotic signal, and a starvation signal] are involved in the control of all these processes that regulate rpoS/sigma S expression.
534 citations
TL;DR: The results support the conclusion that GABAAreceptors are pentamers in which a total of four alternating α and β subunits are connected by a γ subunit.
Abstract: GABAA receptors are ligand-gated chloride ion channels that are presumed to be pentamers composed of α, β, and γ subunits. The subunit stoichiometry, however, is controversial, and the subunit arrangement presently is not known. In this study the ratio of subunits in recombinant α1β3γ2 receptors was determined in Western blots from the relative signal intensities of antibodies directed against the N terminus or the cytoplasmic loop of different subunits after the relative reactivity of these antibodies had been determined with GABAA receptor subunit chimeras composed of the N-terminal domain of one and the remaining part of the other subunit. Via this method a subunit stoichiometry of two α subunits, two β subunits, and one γ subunit was derived. Similar experiments investigating the composition of α1β3 receptors expressed on the surface of human embryonic kidney (HEK) 293 cells cotransfected with α1 and β3 subunits resulted in a stoichiometry of two α and three β subunits. Density gradient centrifugation studies indicated that combinations of α1β3γ2 or α1β3 subunits expressed in HEK 293 cells are able to form pentamers, whereas combinations of α1γ2 or β3γ2 subunits predominantly form heterodimers. These results provide valuable information on the mechanism of GABAAreceptor assembly and support the conclusion that GABAAreceptors are pentamers in which a total of four alternating α and β subunits are connected by a γ subunit.
511 citations
TL;DR: Elp3, the 60-kilodalton subunit of elongator/RNAPII holoenzyme, is identified as a highly conserved histone acetyltransferase (HAT) capable of acetylating core histones in vitro, suggesting a role for a novel, tightly RNAPII-associated HAT in transcription of DNA packaged in chromatin.
495 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2022 | 1 |
| 2020 | 1 |
| 2017 | 9 |
| 2016 | 10 |
| 2015 | 6 |
| 2014 | 7 |