Biology subjects

Lidschreiber, M.

Publications and source records attributed to Lidschreiber, M..

6 recordsLinked to original sources

bioRxiv2025

Structure of human cytoplasmic Pol II complex explains global transcription repression by Gdown1

RNA polymerase II (Pol II) is a 12-subunit enzyme crucial for gene transcription in the nucleus. However, its assembly in the cytoplasm, nuclear import, and nuclear function of assembly factors remain poorly understood. Here, we isolated Pol II from the cytoplasmic fraction of human cells (cfPol II) and determined its cryo-EM structure. The structure reveals that Pol II is fully assembled in the cytoplasm before nuclear import. We also found that Gdown1 binds Pol II through three distinct regions, indicating it may stabilize Pol II assembly intermediates. Notably, Gdown1 binding precludes the association of essential transcription factors IIB and IIF, rendering cfPol II inactive in promoter-dependent transcription in vitro. Our results provide a basis for Gdown1-dependent global transcription repression and suggest a model for the role of Gdown1 in Pol II assembly, import, and transcription regulation.

biochemistry↗

bioRxiv2024

CTCF depletion decouples enhancer-mediated gene activation from chromatin hub formation during cellular differentiation

Enhancers and promoters interact in 3D chromatin structures to regulate gene expression. Here, we characterize the mechanisms that drive the formation of these structures and their function in gene regulation in a lymphoid-to-myeloid transdifferentiation system. Based on analyses at base-pair resolution, we demonstrate a close correlation between binding of regulatory proteins, formation of chromatin interactions, and gene expression. Integration of multi-way interaction analyses and computational modeling shows that tissue-specific gene loci are organized into chromatin hubs, characterized by cooperative interactions between multiple enhancers, promoters, and CTCF-binding sites. Depletion of CTCF strongly impairs the formation of these structures. However, the effects of CTCF depletion on gene expression are modest and can be explained by rewired enhancer-promoter interactions. This demonstrates an instructive role for enhancer-promoter interactions in gene regulation that is independent of cooperative interactions in chromatin hubs. Together, these results contribute to a mechanistic understanding of the structure-function relationship of the genome during cellular differentiation.

genomics↗

bioRxiv2024

Mechanism of Co-Transcriptional Cap-Snatching by Influenza Polymerase

Influenza virus mRNA is stable and competent for nuclear export and translation because it receives a 5' cap(1) structure in a process called cap-snatching1. During cap-snatching, the viral RNA-dependent RNA polymerase (FluPol) binds to host RNA polymerase II (Pol II) and the emerging transcript2,3. The FluPol endonuclease then cleaves a capped RNA fragment that sub-sequently acts as a primer for the transcription of viral genes4,5. Here, we present the cryo-EM structure of FluPol bound to a transcribing Pol II in complex with the elongation factor DSIF in the pre-cleavage state. The structure shows that FluPol directly interacts with both Pol II and DSIF, which position the FluPol endonuclease domain near the RNA exit channel of Pol II. These interactions are important for the endonuclease activity of FluPol and FluPol activity in cells. A second structure trapped after cap-snatching shows that cleavage rearranges the capped RNA primer within the FluPol, directing the capped RNA 3'-end towards the FluPol polymerase active site for viral transcription initiation. Altogether, our results provide the molecular mechanisms of co-transcriptional cap-snatching by FluPol.

biochemistry↗

bioRxiv2021

Oct4 primarily controls enhancer activity rather than accessibility

The transcription factor Oct4 is essential for maintaining stem cell pluripotency and for efficient cell reprogramming, but its functional roles are far from being understood. Here, we investigate the functions of Oct4 by rapidly depleting Oct4 from mouse embryonic stem cells and conducting a time-resolved multiomics analysis. Oct4 depletion leads to an immediate loss of its binding to putative enhancers that are accessible in chromatin. Loss of Oct4 is accompanied by a concomitant decrease in mRNA synthesis from putative target genes that are part of the transcriptional network that maintains pluripotency. Oct4 binding to enhancers does not correlate with chromatin accessibility, whereas Sox2 can apparently retain accessibility after Oct4 depletion even in the absence of eRNA synthesis. These results are consistent with the model that Sox2 primarily acts as a pioneer factor that renders enhancers accessible, whereas Oct4 acts primarily as a transcriptional activator that stimulates transcription of pluripotency enhancers and their target genes.

genomics↗

bioRxiv2021

Sequence determinants of human gene regulatory elements

DNA determines where and when genes are expressed, but the full set of sequence determinants that control gene expression is not known. To obtain a global and unbiased view of the relative importance of different sequence determinants in gene expression, we measured transcriptional activity of DNA sequences that are in aggregate [~]100 times longer than the human genome in three different cell types. We show that enhancers can be classified to three main types: classical enhancers1, closed chromatin enhancers and chromatin-dependent enhancers, which act via different mechanisms and differ in motif content. Transcription factors (TFs) act generally in an additive manner with weak grammar, with classical enhancers increasing expression from promoters by a mechanism that does not involve specific TF-TF interactions. Few TFs are strongly active in a cell, with most activities similar between cell types. Chromatin-dependent enhancers are enriched in forkhead motifs, whereas classical enhancers contain motifs for TFs with strong transactivator domains such as ETS and bZIP; these motifs are also found at transcription start site (TSS)-proximal positions. However, some TFs, such as NRF1 only activate transcription when placed close to the TSS, and others such as YY1 display positional preference with respect to the TSS. TFs can thus be classified into four non-exclusive subtypes based on their transcriptional activity: chromatin opening, enhancing, promoting and TSS determining factors - consistent with the view that the binding motif is the only atomic unit of gene expression.

genomics↗

bioRxiv2018

NASC-seq monitors RNA synthesis in single cells

Sequencing of newly synthesized RNA can monitor transcriptional dynamics with great sensitivity and high temporal resolution, but is currently restricted to populations of cells. Here, we developed newly synthesized alkylation-dependent single-cell RNA sequencing (NASC-seq), to monitor both newly synthesized and pre-existing RNA in single cells. We validated the method on pre-alkylated exogenous spike-in RNA, and by demonstrating that more newly synthesized RNA was detected for genes with known high mRNA turnover. Importantly, NASC-seq reveals rapidly up- and down-regulated genes during the T-cell activation, and RNA sequenced for induced genes were essentially only newly synthesized. Moreover, the newly synthesized and preexisting transcriptomes after T-cell activation were distinct confirming that we indeed could simultaneously measure gene expression corresponding to two time points in single cells. Altogether, NASC-seq is a powerful tool to investigate transcriptional dynamics and it will enable the precise monitoring of RNA synthesis at flexible time periods during homeostasis, perturbation responses and cellular differentiation.

genomics↗