Biology subjects

Struhl, K.

Publications and source records attributed to Struhl, K..

9 recordsLinked to original sources

bioRxiv2024

TRiC/CCT Chaperonin Governs RNA Polymerase II Activity in the Nucleus to Support RNA Homeostasis

The chaperonin TRiC/CCT is a large hetero-oligomeric ringed-structure that is essential in eukaryotes. While present in the nucleus, TRiC/CCT is typically considered to function in the cytosol where it mediates nascent polypeptide folding and the assembly/disassembly of protein complexes. Here, we investigated the nuclear role of TRiC/CCT. Inactivation of TRiC/CCT resulted in a significant increase in the production of nascent RNA leading to the accumulation of noncoding transcripts. The influence on transcription was not due to cytoplasmic TRiC/CCT-activities or other nuclear proteins as the effect was observed when TRiC/CCT was evicted from the nucleus and restricted to the cytoplasm. Rather, our data support a direct role of TRiC/CCT in regulating RNA polymerase II activity, as the chaperonin modulated nascent RNA production both in vivo and in vitro. Overall, our studies reveal a new avenue by which TRiC/CCT contributes to cell homeostasis by regulating the activity of nuclear RNA polymerase II.

molecular biology↗

bioRxiv2022

High level and molecular nature of transcriptional noise in yeast cells

"Biological noise" is defined as functionally insignificant events that occur in living cells due to imperfect fidelity of biological processes. Distinguishing between biological function and biological noise is often difficult, and experiments to measure biological noise have not been performed. Here, we measure biological noise in yeast cells by analyzing chromatin structure and transcription of an 18 kb region of DNA whose sequence was randomly generated and hence lacks biological function. Nucleosome occupancy on random-sequence DNA is comparable to that on yeast genomic DNA. However, nucleosome-depleted regions are much less frequent, and there are fewer well-positioned nucleosomes and shorter nucleosome arrays. Steady-state levels of RNAs expressed from random-sequence DNA are comparable to those of typical yeast mRNAs, although transcription and mRNA decay rates are higher. Transcriptional initiation (5 ends) from random-sequence DNA occurs at numerous sites at low levels, indicating very low intrinsic specificity of the Pol II machinery. In contrast, poly(A) profiles (relative levels and clustering of 3 isoforms) of random-sequence RNAs are roughly comparable to those within 3 untranslated regions of yeast mRNAs, suggesting limited evolutionary constraints on poly(A) site choice. RNAs expressed from random-sequence DNA show higher cell-to-cell variability than RNAs expressed from yeast genomic DNA, suggesting that functional elements limit the variability among individual cells within a population. These observations indicate that transcriptional noise occurs at high levels in yeast, and they provide insight into how chromatin and transcription patterns arise from the evolved yeast genome.

molecular biology↗

bioRxiv2022

Nucleotide level linkage of transcriptional elongation and polyadenylation

Alternative polyadenylation yields many mRNA isoforms whose 3 termini occur disproportionately in clusters within 3 UTRs. Previously, we showed that profiles of poly(A) site usage are regulated by the rate of transcriptional elongation by RNA polymerase (Pol) II (Geisberg et., 2020). Pol II derivatives with slow elongation rates confer an upstream-shifted poly(A) profile, whereas fast Pol II strains confer a downstream-shifted poly(A) profile. In yeast, upstream and downstream shifts within isoform clusters occur steadily at the nucleotide level. In contrast, changes from one isoform to the next are much smaller between clusters, even when the distances between them are relatively large. GC content in a region 13-30 nt downstream from isoform clusters is linked to Pol II elongation rate. In human cells, the upstream shift caused by a slow Pol II mutant also occurs continuously at the nucleotide level within clusters, but not between them. Pol II occupancy increases just downstream of the most speed-sensitive poly(A) sites, suggesting a linkage between reduced elongation rate and cluster formation. These observations suggest that 1) Pol II elongation speed affects the nucleotide-level dwell time allowing polyadenylation to occur, 2) poly(A) site clusters are linked to the local elongation rate and hence do not arise simply by intrinsically imprecise cleavage and polyadenylation of the RNA substrate, 3) DNA sequence elements can affect Pol II elongation and poly(A) profiles, and 4) the cleavage/polyadenylation and Pol II elongation complexes are spatially, and perhaps physically, coupled so that polyadenylation occurs rapidly upon emergence of the nascent RNA from the Pol II elongation complex.

molecular biology↗

bioRxiv2022

MafB, WDR77, and ss-catenin interact with each other and have similar genome association profiles

MafB (a bZIP transcription factor), {beta}-catenin (the ultimate target of the Wnt signal transduction pathway that acts as a transcriptional co-activator of LEF/TCF proteins), and WDR77 (a transcriptional co-activator of multiple hormone receptors) are important for breast cellular transformation. Unexpectedly, these proteins interact directly with each other, and they have similar genomic binding profiles. Furthermore, while some of these common target sites coincide with those bound by LEF/TCF, the majority are located just downstream of transcription initiation sites at a position near paused RNA polymerase (Pol II) and the +1 nucleosome. Occupancy levels of these factors at these promoter-proximal sites are strongly correlated with the level of paused Pol II and transcriptional activity.

molecular biology↗

bioRxiv2021

YAP and TAZ are transcriptional co-activators of AP-1 proteins and STAT3 during breast cellular transformation

The YAP and TAZ paralogues are transcriptional co-activators recruited to target sites, primarily by TEAD proteins. Here, we show that YAP and TAZ are also recruited by JUNB and STAT3, key factors that mediate an epigenetic switch linking inflammation to cellular transformation. YAP and TAZ directly interact with JUNB and STAT3 via a WW domain important for transformation, co-occupy many target sites in vivo via AP-1 and (to a lesser extent) STAT3 sequence motifs, and stimulate transcriptional activation by AP-1 proteins. A few target sites are YAP- or TAZ-specific, and they are associated with different sequence motifs and gene classes. YAP/TAZ, JUNB, and STAT3 directly regulate a common set of target genes that overlap, but are distinct from, those regulated by YAP/TAZ and TEADs. The set of genes regulated by YAP/TAZ, STAT3, and JUNB is associated with poor survival in breast cancer patients with the triple-negative form of the disease.

molecular biology↗

bioRxiv2020

Different SP1 binding dynamics at individual genomic loci in human cells

Using a tamoxifen-inducible time-course ChIP-seq approach, we show that the ubiquitous transcription factor SP1 has different binding dynamics at its target sites in the human genome that are not correlated with SP1 occupancy levels at those sites. While ~70% of SP1 binding sites are located in promoter regions, loci with slow SP1 binding turnover are enriched in enhancer and Polycomb-repressed regions. Unexpectedly, SP1 sites with fast turnover times tend to have higher quality and more copies of the SP1 sequence motif. Different co-binding factors associate near SP1 binding sites depending on their binding kinetics and on their location at promoters or enhancers. For example, NFY and FOS are preferentially associated near promoter-bound SP1 sites with fast turnover, whereas DNA motifs of ETS and homeodomain proteins are preferentially observed at sites with slow turnover. At promoters but not enhancers, proteins involved in sumoylation and PML bodies associate more strongly with slow SP1 binding sites than with the fast-binding sites. The speed of SP1 binding turnover is not associated with nucleosome occupancy, and it is not necessarily coupled to higher transcriptional activity. These results with SP1 are in contrast from those of human TBP, indicating that there is no common mechanism affecting transcription factor binding kinetics.

molecular biology↗

bioRxiv2020

Pheno-RNA, a method to identify genes linked to a specific phenotype: application to cellular transformation

Cellular transformation is associated with dramatic changes in gene expression, but it is difficult to determine which regulated genes are oncogenically relevant. Here, we describe Pheno-RNA, a general approach to identify candidate genes associated with a specific phenotype. Specifically, we generate a "phenotypic series" by treating a non-transformed breast cell line with a wide variety of molecules that induce cellular transformation to various extents. By performing transcriptional profiling across this phenotypic series, the expression profile of every gene can be correlated with the transformed phenotype. We identify ~200 genes whose expression profiles are very highly correlated with the transformation phenotype, strongly suggesting their importance in transformation. Within biological categories linked to cancer, some genes show high correlations with the transformed phenotype, but others do not. Many genes whose expression profiles are highly correlated with transformation have never been linked to cancer, suggesting the involvement of heretofore unknown genes in cancer.

cancer biology↗

bioRxiv2019

Promoter-specific dynamics of TATA-binding protein association with the human genome

Transcription factor binding to target sites in vivo is a dynamic process that involves cycles of association and dissociation, with individual proteins differing in their binding dynamics. The dynamics at individual sites on a genomic scale has been investigated in yeast cells, but comparable experiments have not been done in multicellular eukaryotes. Here, we describe a tamoxifen-inducible, time-course ChIP-seq approach to measure transcription factor binding dynamics at target sites throughout the human genome. As observed in yeast cells, the TATA-binding protein (TBP) typically displays rapid turnover at RNA polymerase (Pol) II-transcribed promoters, slow turnover at Pol III promoters, and very slow turnover at the Pol I promoter. Interestingly, turnover rates vary widely among Pol II promoters in a manner that does not correlate with the level of TBP occupancy. Human Pol II promoters with slow TBP dissociation preferentially contain a TATA consensus motif, support high transcriptional activity of downstream genes, and are linked with specific activators and chromatin remodelers. These properties of human promoters with slow TBP turnover differ from those of yeast promoters with slow turnover. These observations suggest that TBP binding dynamics differentially affect promoter function and gene expression, possibly at the level of transcriptional reinitiation/bursting.

molecular biology↗

bioRxiv2018

Regulatory network controlling tumor-promoting inflammation in human cancers

Using an inducible, inflammatory model of breast cellular transformation, we describe the transcriptional regulatory network mediated by STAT3, NF-{kappa}B, and AP-1 factors on a genomic scale. These regulators form transcriptional complexes that directly regulate the expression of hundreds of genes in oncogenic pathways via a positive feedback loop. This inflammatory feedback loop, which functions to various extents in many types of cancer cells and patient tumors, is the basis for an \"inflammation\" index that defines cancer types by functional criteria. We identify a network of non-inflammatory genes whose expression is well correlated with the cancer inflammatory index. Conversely, the inflammation index is negatively correlated with expression of genes involved in DNA metabolism, and transformation is associated with genome instability. Inflammatory tumors are preferentially associated with infiltrating immune cells that might be recruited to the site of the tumor via inflammatory molecules produced by the cancer cells.

cancer biology↗