Biology subjects

Cherney, R. E.

Publications and source records attributed to Cherney, R. E..

5 recordsLinked to original sources

bioRxiv2025

Correlated protein-RNA associations reveal a requirement for HNRNPU in long-range Polycomb recruitment by the lncRNAs Airn, Kcnq1ot1, and Xist

The lncRNAs Airn and Kcnq1ot1 recruit Polycomb Repressive Complexes (PRCs) and repress genes over multi-megabase genomic intervals, but how they interact with proteins to direct repression remains poorly understood. We conducted formaldehyde-linked RNA-immunoprecipitations of 27 proteins from trophoblast stem cells, using a protocol exhibiting similar signal-to-noise and post-lysis reassociation ratios as CLIP and CLAP. Patterns of protein associations across Airn and Kcnq1ot1 were more similar to each other than to nearly all other transcripts and partitioned to extents that mirrored degree of repression each lncRNA induced, implying connections to mechanism. Indeed, HNRNPU, an essential protein that helps Xist localize to chromatin, was enriched within and required to direct PRC-catalyzed modifications by Airn and Kcnq1ot1, without being required for their localization. Our study provides insights into the role of HNRNPU in lncRNA-mediated gene regulation and reports architectures of protein association across Airn and Kcnq1ot1 relative to the transcriptome at large. Author summaryMammalian genomes express thousands of long noncoding RNAs (lncRNAs). While most remain functionally uncharacterized, a handful are known to regulate genes via epigenetic pathways. Whether or not these known regulatory lncRNAs operate through shared or divergent mechanisms remains unclear. To gain insight, we compared RNA-protein associations across three known regulatory lncRNAs -- Airn, Kcnq1ot1, and Xist -- relative to the broader transcriptome, using a protocol to immunoprecipitate RNA from formaldehyde-crosslinked cells. Benchmarking of our RNA-immunoprecipitation protocol against methods called CLIP and CLAP revealed similar results and complementary strengths among methods. We discovered similarities in RNA-protein associations between Airn and Kcnq1ot1 that nominated them as mechanistically important. One such protein, HNRNPU, was required for Airn and Kcnq1ot1 to coordinate long-range recruitment of Polycomb complexes, without giving the appearance of being required to tether either lncRNA to chromatin, as HNRNPU has been proposed to do for Xist. Our study identifies RNA-protein associations that correlate with long-range gene regulation by lncRNAs and provides new perspectives on the potential mechanisms through which HNRNPU participates in lncRNA-mediated epigenetic control. We also benchmark a protocol to recover RNA-protein interactions that is simple to execute and has complementary strengths relative to other methods.

molecular biology↗

bioRxiv2023

Ectopically expressed Airn lncRNA deposits Polycomb with a potency that rivals Xist

We report that when expressed at similar levels from an isogenic locus, the Airn lncRNA induces Polycomb deposition with a potency that rivals Xist. However, when subject to the same degree of promoter activation, Xist is more abundant and more potent than Airn. Our data definitively demonstrate that the Airn lncRNA is functional and suggest that Xist achieved extreme potency in part by evolving mechanisms to promote its own abundance.

molecular biology↗

bioRxiv2023

A monoclonal antibody raised against human EZH2 cross-reacts with the RNA-binding protein SAFB

The Polycomb Repressive Complex 2 (PRC2) is a conserved enzyme that tri-methylates Lysine 27 on Histone 3 (H3K27me3) to promote gene silencing. PRC2 is remarkably responsive to the expression of certain long noncoding RNAs (lncRNAs). In the most notable example, PRC2 is recruited to the X-chromosome shortly after expression of the lncRNA Xist begins during X-chromosome inactivation. However, the mechanisms by which lncRNAs recruit PRC2 to chromatin are not yet clear. We report that a broadly used rabbit monoclonal antibody raised against human EZH2, a catalytic subunit of PRC2, cross-reacts with an RNA-binding protein called Scaffold Attachment Factor B (SAFB) in mouse embryonic stem cells (ESCs) under buffer conditions that are commonly used for chromatin immunoprecipitation (ChIP). Knockout of EZH2 in ESCs demonstrated that the antibody is specific for EZH2 by western blot (no cross-reactivity). Likewise, comparison to previously published datasets confirmed that the antibody recovers PRC2-bound sites by ChIP-Seq. However, RNA-IP from formaldehyde-crosslinked ESCs using ChIP wash conditions recovers distinct peaks of RNA association that co-localize with peaks of SAFB and whose enrichment disappears upon knockout of SAFB but not EZH2. IP and mass spectrometry-based proteomics in wild-type and EZH2 knockout ESCs confirm that the EZH2 antibody recovers SAFB in an EZH2-independent manner. Our data highlight the importance of orthogonal assays when studying interactions between chromatin-modifying enzymes and RNA.

molecular biology↗

bioRxiv2022

SAFB associates with nascent RNAs to promote gene expression in mouse embryonic stem cells

Scaffold Attachment Factor B (SAFB) is a conserved RNA Binding Protein (RBP) that is essential for early mammalian development. However, the RNAs that associate with SAFB in mouse embryonic stem cells have not been characterized. Here, we addressed this unknown using RNA-seq and SAFB RNA immunoprecipitation followed by RNA-seq (RIP-seq) in wild-type ESCs and in ESCs in which SAFB and SAFB2 were knocked out. SAFB predominantly associated with introns of protein-coding genes through purine-rich motifs. The transcript most enriched in SAFB association was the lncRNA Malat1, which also contains a purine-rich region in its 5' end. Knockout of SAFB/2 led to down- and upregulation of approximately 1,000 genes associated with multiple biological processes, including genes that are regulated by Polycomb and genes involved in apoptosis, cell division, and cell migration. The spliced and nascent transcripts of many downregulated genes associated with high levels of SAFB in wild-type cells, implying that SAFB binding promotes their expression. Reintroduction of SAFB into double-knockout cells restored gene expression towards wild-type levels, an effect that was again observable at the level of spliced and nascent transcripts. Proteomics analysis revealed a significant enrichment of nuclear speckle-associated and RS-domain containing proteins among SAFB interactors. Our findings suggest that among other potential functions in mouse embryonic stem cells, SAFB promotes the expression of a subset of genes through its ability to bind purine regions in nascent RNA.

molecular biology↗

bioRxiv2020

Elements at the 5' end of Xist harbor SPEN-independent transcriptional antiterminator activity

The Xist lncRNA requires Repeat A, a conserved RNA element located in its 5' end, to induce gene silencing during X-chromosome inactivation. Intriguingly, Repeat A is also required for the production of Xist. While silencing by Repeat A requires the protein SPEN, how Repeat A promotes Xist production remains unclear. We report that in mouse embryonic stem cells, expression of a transgene comprising the first two kilobases of Xist (Xist-2kb) causes transcriptional readthrough of multiple downstream polyadenylation sequences. Readthrough required Repeat A and the ~750 nucleotides downstream but did not require SPEN. Despite associating with SPEN and chromatin, Xist-2kb did not robustly silence transcription, whereas a transgene comprising Xists first 5.5 kilobases robustly silenced transcription and read through its polyadenylation sequence. Longer, spliced Xist transgenes also induced robust silencing yet terminated efficiently. Thus, in contexts examined here, Xist requires sequence elements beyond its first two kilobases to robustly silence transcription, and the 5' end of Xist harbors SPEN-independent transcriptional antiterminator activity that can repress proximal cleavage and polyadenylation. In endogenous contexts, this antiterminator activity may help produce full-length Xist RNA while rendering the Xist locus resistant to silencing by the same repressive complexes that the lncRNA recruits to other genes.

molecular biology↗