Project description:TFIID is a central player in activated transcription initiation. Recent evidence suggests that the role and composition of TFIID is more diverse than previously understood. To investigate the effects of changing the composition of TFIID in a simple system we depleted TAF1 from Drosophila cells and determined the consequences on metal induced transcription at an inducible gene, Metallothionein B (MtnB). We observe a marked increase in the levels of both the mature message and pre-mRNA in TAF1 depleted cells. Under conditions of continued metal exposure, we show that TAF1 depletion increases the magnitude of the initial transcription burst, but has no effect on the timing of that burst. We also show that TAF1 depletion causes delay in the shut-off of transcription upon removal of the stimulus. Thus TAFs are involved in both establishing an upper limit of transcription during induction and efficiently turning the gene off once the inducer is removed. Using genomewide nascent-seq we identify hundreds of genes that are controlled in a similar manner indicating that the findings at this inducible gene are likely generalizable to a large set of promoters. There is a long-standing appreciation for the importance of the spatial and temporal control of transcription. Here we uncover an important third dimension of control, the magnitude of the response. Our results show that the magnitude of the transcriptional response to the same signaling event, even at the same promoter, can vary greatly depending on the composition of the TFIID complex in the cell. Nascent RNA was sequenced from replicate samples of Drosophila S2 cells treated with double-stranded RNA directed against E. coli LacI (Control) or against Drosophlia TAF1 (experimental). Reads per kilo-base per million (RPKM) was determined for each gene and the control and experimental samples were compared to determine the genes that were affected by the depletion of TAF1.
Project description:TFIID is a central player in activated transcription initiation. Recent evidence suggests that the role and composition of TFIID is more diverse than previously understood. To investigate the effects of changing the composition of TFIID in a simple system we depleted TAF1 from Drosophila cells and determined the consequences on metal induced transcription at an inducible gene, Metallothionein B (MtnB). We observe a marked increase in the levels of both the mature message and pre-mRNA in TAF1 depleted cells. Under conditions of continued metal exposure, we show that TAF1 depletion increases the magnitude of the initial transcription burst, but has no effect on the timing of that burst. We also show that TAF1 depletion causes delay in the shut-off of transcription upon removal of the stimulus. Thus TAFs are involved in both establishing an upper limit of transcription during induction and efficiently turning the gene off once the inducer is removed. Using genomewide nascent-seq we identify hundreds of genes that are controlled in a similar manner indicating that the findings at this inducible gene are likely generalizable to a large set of promoters. There is a long-standing appreciation for the importance of the spatial and temporal control of transcription. Here we uncover an important third dimension of control, the magnitude of the response. Our results show that the magnitude of the transcriptional response to the same signaling event, even at the same promoter, can vary greatly depending on the composition of the TFIID complex in the cell.
Project description:General transcription factor TFIID is a cornerstone of RNA polymerase II transcription initiation in eukaryotic nuclei. Human TFIID is a megadalton-sized multiprotein complex composed of the TATA-binding protein (TBP) and 13 TBP-associated factors (TAFs). The cellular mechanism of TFIID assembly is poorly understood. In the cytoplasm of human cells, we discovered a heterotrimeric TFIID sub-complex consisting of the TAF2, TAF8 and TAF10 proteins. Native mass-spectrometry uncovered the interactions between the TAFs, defining a central role of TAF8 in nucleating the complex. X-ray crystallography revealed a non-canonical arrangement of the TAF8-TAF10 histone fold domains (HFDs). TAF2 binds to multiple motifs within the TAF8 C-terminal region, and these interactions dictate TAF2 incorporation into a core-TFIID complex that exists in the nucleus. Our results provide evidence for a step-wise assembly pathway of nuclear holo-TFIID, regulated by nuclear import of preformed cytoplasmic submodules.
Project description:The human general transcription factor TFIID is composed of the TATA-binding protein (TBP) and 13 TBP-associated factors (TAFs). In eukaryotic cells, TFIID nucleates RNA Polymerase II (Pol II) preinitiation complex formation on gene promoters and thus, is crucial for Pol II transcription. Germline knock out of several mouse TFIID subunits (Tbp, Taf7, Taf8, and Taf10) results in lethality at embryonic day 4.0, demonstrating the fundamental role of holo-TFIID in transcription. We identified a child harboring a splice-site mutation in TAF8, who has intellectual disability, poor growth, progressive spasticity and microcephaly. The c.781-G>A TAF8 mutation in this patient resulted in a frame shift, which affected the final 50 carboxy terminal amino acids of TAF8. We found that the mutant TAF8 protein is unstable and the patient c.781-G>A TAF8 primary fibroblasts did not form canonical TFIID complexes. Astonishingly however, genome-wide RNA pol II occupancy and pre-mRNA transcription on the tested genes was unaffected in the patient’s primary fibroblasts. This study indicates that perturbed TFIID function is less deleterious for transcription in human cells than originally anticipated.
Project description:TFIID is a cornerstone of eukaryotic gene regulation. Distinct TFIID complexes with unique subunit composition exist and several TFIID subunits are shared with other complexes, conveying intricate cellular decision making to control subunit allocation and functional assembly of this essential transcription factor. However, the underlying molecular mechanisms remain poorly understood. Here, we used quantitative proteomics to examine TFIID submodules and assembly mechanisms in human cells. Structural and mutational analysis of the cytoplasmic TAF5/TAF6/TAF9 submodule identified novel interactions crucial for TFIID integrity, and for allocating TAF9 to TFIID or the SAGA co-activator complex. We discover a key checkpoint function for the chaperonin CCT, which specifically associates with nascent TAF5 for subsequent handover to TAF6/TAF9 and ultimate holo-TFIID formation. Our findings illustrate at the molecular level how multisubunit complexes are crafted in the cell, involving checkpoint decisions facilitated by a chaperone machine.
Project description:TFIID is a cornerstone of eukaryotic gene regulation. Distinct TFIID complexes with unique subunit composition exist and several TFIID subunits are shared with other complexes, conveying intricate cellular decision making to control subunit allocation and functional assembly of this essential transcription factor. However, the underlying molecular mechanisms remain poorly understood. Here, we used quantitative proteomics to examine TFIID submodules and assembly mechanisms in human cells. Structural and mutational analysis of the cytoplasmic TAF5/TAF6/TAF9 submodule identified novel interactions crucial for TFIID integrity, and for allocating TAF9 to TFIID or the SAGA co-activator complex. We discover a key checkpoint function for the chaperonin CCT, which specifically associates with nascent TAF5 for subsequent handover to TAF6/TAF9 and ultimate holo-TFIID formation. Our findings illustrate at the molecular level how multisubunit complexes are crafted in the cell, involving checkpoint decisions facilitated by a chaperone machine.
Project description:Previous studies suggested that expression of most yeast mRNAs is dominated by either transcription factor TFIID or SAGA. We reexamined this longstanding problem by rapid depletion of TFIID subunits and measurement of changes in nascent transcription. We find that transcription of nearly all mRNAs is strongly dependent on TFIID function. Degron-dependent depletion of Tafs 1,2,7,11, and 13 showed similar transcription decreases for genes in the Taf1-depleted, Taf1-enriched, TATA-containing and TATA-less gene classes. The magnitude of TFIID-dependence varies with growth conditions, although this variation is similar at all gene classes. Many studies have suggested differences in gene regulatory mechanisms between TATA and TATA-less genes and these differences have been attributed in part to differential dependence on SAGA or TFIID. Our work indicates that TFIID contributes significantly to expression of nearly all yeast mRNAs and that differences in regulation between these two gene classes is due to other properties.
Project description:microRNAs (miRNAs) are a class of small non-coding RNAs involved in the coordination and/or fine-tuning of gene expression. As such, miRNAs are thought to be critical cis-acting regulatory factors that control a wide range of physiological processes in the brain. The datasets presented here represent the miRNA transcriptome of the adult and larval Drosophila melanogaster CNS as determined by small RNA deep sequencing (RNA-Seq). They were derived from adult and larval samples explanted from the animal that contain minimal extraneous (non-neuronal) tissues. Here we present a concise summary of our profiling results as well as the original sequencing data. We identify many miRNAs that are expressed at equal levels in both tissues and several that are significantly enriched in the larval and adult brain. Some of these belong to miRNA families with conserved members in mammals. These datasets should provide a good starting point for others interested in characterizing miRNAs with putative functions in Drosophila neurons.
Project description:microRNAs (miRNAs) are a class of small non-coding RNAs involved in the coordination and/or fine-tuning of gene expression. As such, miRNAs are thought to be critical cis-acting regulatory factors that control a wide range of physiological processes in the brain. The datasets presented here represent the miRNA transcriptome of the adult and larval Drosophila melanogaster CNS as determined by small RNA deep sequencing (RNA-Seq). They were derived from adult and larval samples explanted from the animal that contain minimal extraneous (non-neuronal) tissues. Here we present a concise summary of our profiling results as well as the original sequencing data. We identify many miRNAs that are expressed at equal levels in both tissues and several that are significantly enriched in the larval and adult brain. Some of these belong to miRNA families with conserved members in mammals. These datasets should provide a good starting point for others interested in characterizing miRNAs with putative functions in Drosophila neurons. The datasets presented here represent the miRNA transcriptome of the adult and larval Drosophila melanogaster CNS as determined by small RNA deep sequencing (RNA-Seq).