Biology subjects

Szczurek, A. T.

Publications and source records attributed to Szczurek, A. T..

3 recordsLinked to original sources

bioRxiv2023

Polycomb sustains promoters in a deep OFF-state by limiting PIC formation to counteract transcription

The Polycomb system plays fundamental roles in regulating gene expression during mammalian development. However, how it controls transcription to enable gene repression has remained enigmatic. Here we employ rapid degron-based depletion coupled with live-cell transcription imaging and single-particle tracking to uncover how the Polycomb system controls transcription in single cells. We discover that the Polycomb system is not a constitutive block to transcription but instead sustains a long-lived deep promoter OFF-state which limits the frequency with which the promoter can enter into a transcribing state. We demonstrate that Polycomb sustains this deep promoter OFF-state by counteracting the binding of factors that enable early transcription pre-initiation complex formation and show that this is necessary for gene repression. Together these important discoveries provide a new rationale for how the Polycomb system controls transcription and suggests a universal mechanism that could enable the Polycomb system to constrain transcription across diverse cellular contexts.

cell biology↗

bioRxiv2022

A CpG island-encoded mechanism protects genes from premature transcription termination

Transcription must be highly controlled to regulate gene expression and development. However, our understanding of the molecular mechanisms that influence transcription and how these are coordinated in cells to ensure normal gene expression remains rudimentary. Here, we reveal that actively transcribed CpG island-associated gene promoters recruit SET1 chromatin modifying complexes to enable gene expression. Counterintuitively, this effect is independent of SET1 complex histone modifying activity, and instead relies on the capacity of these complexes to interact with the RNA Polymerase II-binding protein, WDR82. Unexpectedly, we discover that SET1 complexes sustain gene transcription by counteracting the activity of the ZC3H4/WDR82 protein complex, which we show can pervasively terminate both genic and extragenic transcription. Therefore, we discover a new gene regulatory mechanism whereby CpG island elements nucleate a protein complex that protects genic transcription from premature termination, effectively distinguishing genic from non-genic transcription to enable gene expression.

molecular biology↗

bioRxiv2020

PRC1 drives Polycomb-mediated gene repression by controlling transcription initiation and burst frequency

The Polycomb repressive system plays a fundamental role in controlling gene expression during mammalian development. To achieve this, Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) bind target genes and use histone modification-dependent feedback mechanisms to form Polycomb chromatin domains and repress transcription. The interrelatedness of PRC1 and PRC2 activity at these sites has made it difficult to discover the specific components of Polycomb chromatin domains that drive gene repression and to understand mechanistically how this is achieved. Here, by exploiting rapid degron-based approaches and time-resolved genomics we kinetically dissect Polycomb-mediated repression and discover that PRC1 functions independently of PRC2 to counteract RNA polymerase II binding and transcription initiation. Using single-cell gene expression analysis, we reveal that PRC1 acts uniformly within the cell population, and that repression is achieved by controlling transcriptional burst frequency. These important new discoveries provide a mechanistic and conceptual framework for Polycomb-dependent transcriptional control.

molecular biology↗