Biology subjects

Embree, C. M.

Publications and source records attributed to Embree, C. M..

4 recordsLinked to original sources

bioRxiv2026

eIF4E and Ezrin cooperate in pseudopods to drive a localized migratory translation program in acute myeloid leukemia

Aggressive subtypes of acute myeloid leukemia (AML) are characterized by increased migratory behavior and poor prognosis prioritizing the need for uncovering relevant mechanisms. While attributed to transcriptional changes, these AMLs manifest dysregulated eIF4E implicating disrupted mRNA metabolism. Here, we observed in AML mouse models, patient specimens, and cell lines that eIF4E drives motility, colonization, engraftment and AML progression. AML cells migrate utilizing Ezrin-positive pseudopods. Unexpectedly, we discovered that eIF4E interacts with Ezrin, that these physically associated factors are required and cooperated to drive an on-demand translation program in pseudopods for motility. Indeed, pseudopods were sites of eIF4E- and Ezrin-dependent translation by implementing the first method to directly mark active ribosomes in situ (Visualizing Translation Activity using RiboLace, VISTA-R). Biochemically, Ezrin bound eIF4E, ribosomal components, and mRNAs consistent with our observed Ezrin-dependent modulation of protein production. This unprecedented physical coupling of motility and translation provisions migratory sites to sustain AML progression. Highlights- eIF4E reduction impairs AML cell motility and disease progression - eIF4E-dependent motility requires Ezrin - Ezrin binds eIF4E, transcripts encoding motility factors and active ribosomes - VISTA-R enabled visualization of active ribosomes and translationally active pseudopods (T-PODs) - T-PODs provide novel on-demand localized translation to sustain mobility at migratory sites Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=142 SRC="FIGDIR/small/707190v2_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@164f191org.highwire.dtl.DTLVardef@2f8928org.highwire.dtl.DTLVardef@d5ad7forg.highwire.dtl.DTLVardef@719a69_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2025

Nuclear RNA cap-chaperones eIF4E and NCBP2 govern distinct fates for 1000s of mRNAs uncovering an unexpected regulatory point in gene expression

mRNA processing constitutes a series of steps in the nucleus to generate mature mRNAs that can be translated into protein. This relies on the methyl-7-guanosine (m7G) "cap" on the 5end of mRNAs which is bound by the nuclear cap-binding protein NCBP2 with its cofactor NCBP1. The NCBP1/2 complex chaperones capped mRNA through these processing steps. NCBP2 is considered the sole nuclear cap-binding factor and thus its cap-chaperone role is thought to be a constitutive, housekeeping activity. However, another cap-binding protein, the eukaryotic translation initiation factor eIF4E, is also found in the nucleus. Two cap-binding factors co-existing in the nucleus intimate an undiscovered regulatory point in gene expression or, alternatively, redundancy to ensure gene expression fidelity. Consistent with the former possibility, eIF4E and NCBP2 drove distinct gene expression, transcriptomic, and splicing signatures impacting [~]2500 transcripts involved in distinct biological programmes with only [~]360 transcripts in common and of these only 79 common splicing events. Thus, each cap-chaperone designates distinct mRNA populations for specific processing revealing a new step in gene expression. We denote this mRNA specification of cap-chaperones (SOCCS). We uncovered multiple molecular mechanisms that contribute to SOCCS: distinct spatial localization of eIF4E and NCBP2 within the nucleus, identification of sequence motifs within targeted mRNAs segregated by eIF4E or NCBP2 sensitivity, distinct protein partners for these cap-chaperones and differential impacts on the production of key spliceosome components e.g. U2AF1, PRP31, SF3B1 and SNRNP200 indicative of distinct transcriptomic landscapes produced by eIF4E or NCBP2 overexpression. In all, the realization that multiple cap-binding proteins coexist in the nucleus led us to identify an unexpected gene-expression regulatory point which engaged distinct biological programmes.

genetics↗

bioRxiv2024

Direct and indirect effects of spliceosome disruption compromise gene regulation by Nonsense-Mediated mRNA Decay

Pre-mRNA splicing, carried out in the nucleus by a large ribonucleoprotein machine known as the spliceosome, is functionally and physically coupled to the mRNA surveillance pathway in the cytoplasm called nonsense mediated mRNA decay (NMD). The NMD pathway monitors for premature translation termination signals, which can result from alternative splicing, by relying on the exon junction complex (EJC) deposited on exon-exon junctions by the spliceosome. Recently, multiple genetic screens in human cell lines have identified numerous spliceosome components as putative NMD factors. Using publicly available RNA-seq datasets from K562 and HepG2 cells depleted of 18 different spliceosome components, we find that natural NMD targeted mRNA isoforms are upregulated when members of the catalytic spliceosome are reduced. While some of this increase could be due to widespread pleiotropic effects of spliceosome dysfunction (e.g., reduced expression of NMD factors due to mis-splicing of their mRNAs), we identify that AQR, SF3B1, SF3B4 and CDC40 may have a more direct role in NMD. We also test the hypothesis that increased production of novel NMD substrates may overwhelm the pathway to find a direct correlation between the amount of novel NMD substrates detected and the degree of NMD inhibition observed. Finally, similar transcriptome alterations and NMD substrate upregulation are also observed in cells treated with spliceosome inhibitors and in cells derived from retinitis pigmentosa patients with mutations in PRPF8 and PRPF31. Overall, our results show that regardless of the cause, spliceosome disruption upregulates a broad set of NMD targets, which could contribute to cellular dysfunction in spliceosomopathies. AUTHOR SUMMARYDuring gene expression, a complex cellular machine known as spliceosome removes extraneous non-coding sequences from precursor RNAs to produce messenger RNA (mRNA) with a contiguous code for protein sequence. To guard against splicing errors that may interrupt protein coding sequence, splicing is linked to a mRNA surveillance pathway known as nonsense mediated mRNA decay (NMD). In this work, we follow up on recent findings from multiple genetic screens that several spliceosome components are necessary for efficient NMD. Our analysis of transcriptomes of lymphoblast K562 cells depleted of 18 spliceosome factors show that NMD based regulation is compromised in cells lacking catalytic spliceosome proteins. Four of these spliceosome proteins may have a direct effect on NMD even though spliceosome disruption in general also causes other changes in gene expression that indirectly affect NMD. Our results suggest that defective NMD based regulation contributes to cellular dysfunction in spliceosomopathies, a collection of human genetic disorders caused by mutations in spliceosome factors.

molecular biology↗

bioRxiv2024

Sm-site containing mRNAs can accept Sm-rings and are downregulated in Spinal Muscular Atrophy

Sm-ring assembly is important for the biogenesis, stability, and function of uridine-rich small nuclear RNAs (U snRNAs) involved in pre-mRNA splicing and histone pre-mRNA processing. Sm-ring assembly is cytoplasmic and dependent upon the Sm-site sequence and structural motif, ATP, and Survival motor neuron (SMN) protein complex. While RNAs other than U snRNAs were previously shown to associate with Sm proteins, whether this association follows Sm-ring assembly requirements is unknown. We systematically identified Sm-sites within the human and mouse transcriptomes and assessed whether these sites can accept Sm-rings. In addition to snRNAs, Sm-sites are highly prevalent in the 3 untranslated regions of long messenger RNAs. RNA immunoprecipitation experiments confirm that Sm-site containing mRNAs associate with Sm proteins in the cytoplasm. In modified Sm-ring assembly assays, Sm-site containing RNAs, from either bulk polyadenylated RNAs or those transcribed in vitro, specifically associate with Sm proteins in an Sm-site and ATP-dependent manner. In cell and animal models of Spinal Muscular Atrophy (SMA), mRNAs containing Sm-sites are downregulated, suggesting reduced Sm-ring assembly on these mRNAs may contribute to SMA pathogenesis. Together, this study establishes that Sm-site containing mRNAs can accept Sm-rings and identifies a novel mechanism for Sm proteins in regulation of cytoplasmic mRNAs. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=196 SRC="FIGDIR/small/617433v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@d50f03org.highwire.dtl.DTLVardef@1cca1dforg.highwire.dtl.DTLVardef@1976fcaorg.highwire.dtl.DTLVardef@12c41d9_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗