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The human general transcription factor TFIID is composed of the TATA-binding protein (TBP) and 13 TBP-associated factors (TAFs). In eukaryotic cells, TFIID is thought to nucleate RNA polymerase II (Pol II) preinitiation complex formation on all protein coding gene promoters and thus, be crucial for Pol II transcription. TFIID is composed of three lobes, named A, B, and C. A 5TAF core complex can be assembled in vitro constituting a building block for the further assembly of either lobe A or B in TFIID. Structural studies showed that TAF8 forms a histone fold pair with TAF10 in lobe B and participates in connecting lobe B to lobe C. To better understand the role of TAF8 in TFIID, we have investigated the requirement of the different regions of TAF8 for the in vitro assembly of lobe B and C and the importance of certain TAF8 regions for mouse embryonic stem cell (ESC) viability. We have identified a region of TAF8 distinct from the histone fold domain important for assembling with the 5TAF core complex in lobe B. We also delineated four more regions of TAF8 each individually required for interacting with TAF2 in lobe C. Moreover, CRISPR/Cas9-mediated gene editing indicated that the 5TAF core-interacting TAF8 domain and the proline-rich domain of TAF8 that interacts with TAF2 are both required for mouse embryonic stem cell survival. Thus, our study defines distinct TAF8 regions involved in connecting TFIID lobe B to lobe C that appear crucial for TFIID function and consequent ESC survival., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Dehydration responsive element binding (DREB) factors or CRT element binding factors (CBFs) are members of the AP2/ERF family, which comprises a large number of stress-responsive regulatory genes. This review traverses almost two decades of research, from the discovery of DREB/CBF factors to their optimization for application in plant biotechnology. In this review, we describe (i) the discovery, classification, structure, and evolution of DREB genes and proteins; (ii) induction of DREB genes by abiotic stresses and involvement of their products in stress responses; (iii) protein structure and DNA binding selectivity of different groups of DREB proteins; (iv) post-transcriptional and post-translational mechanisms of DREB transcription factor (TF) regulation; and (v) physical and/or functional interaction of DREB TFs with other proteins during plant stress responses. We also discuss existing issues in applications of DREB TFs for engineering of enhanced stress tolerance and improved performance under stress of transgenic crop plants., (© The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Main Conclusion: SbMYB15, R2R3-type MYB was induced by the different stresses, and conferred stress tolerance in transgenic tobacco by regulating the expression of stress-responsive genes. MYBs are the master regulators of various metabolic processes and stress responses in plants. In this study, we functionally characterised a R2R3-type SbMYB15 transcription factor (TF) from the extreme halophyte Salicornia brachiata. The SbMYB15 acts as a transcriptional activator. Transcriptional analysis showed that SbMYB15 transcript was strongly upregulated in red shoots and was also induced by different stresses; however, its expression remained unchanged with ABA. Overexpression of SbMYB15 in tobacco significantly improved salinity and dehydration tolerance. The enhanced tolerance of the transgenic plants was defined by the changes in chlorophyll, malondialdehyde (MDA), proline, total soluble sugar and total amino acid contents. The transgenic plants exhibited a higher membrane stability and reduced electrolyte leakage, H2O2 and O 2 (-) content compared to the wild type (WT). With ionic stress, transgenics showed a low Na(+) and a high K(+) content. In the transgenic plants, the expression of stress-responsive genes such as LEA5, ERD10D, PLC3, LTP1, HSF2, ADC, P5CS, SOD and CAT was enhanced in the presence of salinity, dehydration and heat. Exposure to gradual salinity and dehydration resulted in an increased stomatal conductance, water use efficiency, photosynthesis rate, photochemical quenching and reduced transpiration rate. Thus, SbMYB15 served as an important mediator of stress responses regulating different stress signalling pathways, leading to enhanced stress tolerance.

Dehydration-responsive element binding (DREB) transcription factor (TF) plays a key role for abiotic stress tolerance in plants. Earlier, we have published the isolation and characterisation of an A-2-type SbDREB2A TF from an extreme halophyte Salicornia brachiata. The SbDREB2A protein lacks potential proline (P), glutamic acid (E), serine (S) and threonine (T) (PEST) sequence which is known to act as signal peptide for protein degradation. In this study, SbDREB2A TF was over-expressed in tobacco plants without any modification in polypeptide sequence. Transgenic plants showed better seed germination and growth characteristics in both hyperionic and hyperosmotic stresses. Transgenic plants exhibited higher water content, membrane stability and less electrolyte leakage in stress conditions. The transgenic plants accumulated less Na(+) and higher K(+) than wildtype (WT) plants. The transgenic plants revealed higher chlorophyll content, water use efficiency (WUE) and net photosynthesis rate. Transgenics exhibited higher level of proline and low amount of MDA and H2O2 under stress conditions. The real-time PCR of transgenics showed higher expression of downstream heat shock genes (Hsp18, Hsp26 and Hsp70), TFs (AP2 domain containing TF, HSF2 and ZFP), signalling components (PLC3 and Ca (2+) /calmodulin) and dehydrins (ERD10B, ERD10D and LEA5) under different abiotic stress treatments.

Dehydration-responsive element binding (DREB) transcription factor plays a key role in plant stress signal transduction pathway. In this study, SbDREB2A has been isolated from the halophyte Salicornia brachiata. SbDREB2A cDNA is 1,062 bp long, encoding protein of 353 amino acids with an estimated molecular mass of 39.37 kDa and a pI of 4.98. On the basis of multiple sequence alignment and phylogenetic analysis, SbDREB2A is classified in A-2 group of the DREB family. The genomic organization confirms that SbDREB2A is an intronless gene. Purified recombinant SbDREB2A protein showed similar binding to both DREs (dehydration-responsive element), ACCGAC and GCCGAC. The transcript expression of SbDREB2A was induced by NaCl, drought and heat stress. The role of SbDREB2A in abiotic stress was studied in E. coli BL21 (DE3). The recombinant E. coli cells exhibited better growth in basal LB medium as well as in supplemented with NaCl, PEG and mannitol. The enhanced growth in recombinant E. coli could be due to the regulation of stress regulated functional genes by this transcription factor. This system can be applied in biotechnological applications, where growth of E. coli can be enhanced under salt stress for efficient recombinant protein production in a short span of time.

During oocyte growth, transcription is required to create RNA and protein reserves to achieve maternal competence. During this period, the general transcription factor TATA binding protein (TBP) is replaced by its paralogue, TBPL2 (TBP2 or TRF3), which is essential for RNA polymerase II transcription. We show that in oocytes TBPL2 does not assemble into a canonical TFIID complex. Our transcript analyses demonstrate that TBPL2 mediates transcription of oocyte-expressed genes, including mRNA survey genes, as well as specific endogenous retroviral elements. Transcription start site (TSS) mapping indicates that TBPL2 has a strong preference for TATA-like motif in core promoters driving sharp TSS selection, in contrast with canonical TBP/TFIID-driven TATA-less promoters that have broader TSS architecture. Thus, we show a role for the TBPL2/TFIIA complex in the establishment of the oocyte transcriptome by using a specific TSS recognition code. The vertebrate TATA-binding protein (TBP) paralogue (TBPL2) is only expressed in growing oocytes, where TBP is absent. Here the authors highlight a unique role for the TBPL2/TFIIA complex in the establishment of the oocyte transcriptome by using a specific TSS recognition code. [ABSTRACT FROM AUTHOR]

The TATA-binding protein (TBP) and a transcription factor (TF) IIB-like factor are important constituents of all eukaryotic initiation complexes. The reason for the emergence and strict requirement of the additional initiation factor Bdp1 in the RNA polymerase (RNAP) III system, however, remained elusive. A poorly studied aspect in this context is the effect of DNA strain arising from DNA compaction and transcriptional activity on initiation complex formation. We made use of a DNA origami-based force clamp to follow the assembly of human initiation complexes in the RNAP II and RNAP III systems at the single-molecule level under piconewton forces. We demonstrate that TBP-DNA complexes are force-sensitive and TFIIB is sufficient to stabilise TBP on a strained promoter. In contrast, Bdp1 is the pivotal component that ensures stable anchoring of initiation factors, and thus the polymerase itself, in the RNAP III system. Thereby, we offer an explanation for the crucial role of Bdp1 for the high transcriptional output of RNAP III. TATA-binding protein (TBP) and a transcription factor (TF) IIB-like factor are important constituents of all eukaryotic initiation complexes. Here, the authors use a DNA origami-based force clamp to investigate the assembly dynamics of human initiation complexes in the RNAP II and RNAP III systems at the single-molecule level under pico newton forces. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cryo-EM structures illuminate human TFIID plasticity. [•] TAF1–TBP crystal structure reveals regulatory roles of TAF1 in transcription. [•] RNAPII–TFIIB initially transcribing complex (ITC) structure details TFIIB function. [•] Crystal structures of the Mediator head module were elucidated. [•] EM studies reveal principles of yeast and human PIC assembly. [ABSTRACT FROM AUTHOR]

RNA polymerase II (RNAPII) transcription is governed by the pre-initiation complex (PIC), which contains TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIH, RNAPII, and Mediator. After initiation, RNAPII enzymes pause after transcribing less than 100 bases; precisely how RNAPII pausing is enforced and regulated remains unclear. To address specific mechanistic questions, we reconstituted human RNAPII promoter-proximal pausing in vitro , entirely with purified factors (no extracts). As expected, NELF and DSIF increased pausing, and P-TEFb promoted pause release. Unexpectedly, the PIC alone was sufficient to reconstitute pausing, suggesting RNAPII pausing is an inherent PIC function. In agreement, pausing was lost upon replacement of the TFIID complex with TATA-binding protein (TBP), and PRO-seq experiments revealed widespread disruption of RNAPII pausing upon acute depletion (t = 60 min) of TFIID subunits in human or Drosophila cells. These results establish a TFIID requirement for RNAPII pausing and suggest pause regulatory factors may function directly or indirectly through TFIID. • Reconstitution of RNAPII pausing in vitro , with purified factors (no extracts) • Human PIC alone is sufficient to establish RNAPII pausing • TFIID is required for RNAPII promoter-proximal pausing • Rapid TFIID depletion induces RNAPII pause release genome-wide Fant and co-workers use biochemical reconstitution to discover that the general transcription factor TFIID is required to establish RNAPII promoter-proximal pausing; canonical regulatory factors NELF and DSIF enhance pausing but are not required. Follow-up experiments in human and Drosophila cells show TFIID is a conserved regulator of RNAPII pausing. [ABSTRACT FROM AUTHOR]