Protein arginine methyltransferase (PRMT) 5 is over-expressed in a variety of cancers and the master transcription regulator E2F1 is an important methylation target. We have explored the role of ...PRMT5 and E2F1 in regulating the non-coding genome and report here a striking effect on long non-coding (lnc) RNA gene expression. Moreover, many MHC class I protein-associated peptides were derived from small open reading frames in the lncRNA genes. Pharmacological inhibition of PRMT5 or adjusting E2F1 levels qualitatively altered the repertoire of lncRNA-derived peptide antigens displayed by tumour cells. When presented to the immune system as either ex vivo-loaded dendritic cells or expressed from a viral vector, lncRNA-derived peptides drove a potent antigen-specific CD8 T lymphocyte response, which translated into a significant delay in tumour growth. Thus, lncRNA genes encode immunogenic peptides that can be deployed as a cancer vaccine.
E2F transcription factors are implicated in diverse cellular functions. The founding member, E2F‐1, is endowed with contradictory activities, being able to promote cell‐cycle progression and induce ...apoptosis. However, the mechanisms that underlie the opposing outcomes of E2F‐1 activation remain largely unknown. We show here that E2F‐1 is directly methylated by PRMT5 (protein arginine methyltransferase 5), and that arginine methylation is responsible for regulating its biochemical and functional properties, which impacts on E2F‐1‐dependent growth control. Thus, depleting PRMT5 causes increased E2F‐1 protein levels, which coincides with decreased growth rate and associated apoptosis. Arginine methylation influences E2F‐1 protein stability, and the enhanced transcription of a variety of downstream target genes reflects increased E2F‐1 DNA‐binding activity. Importantly, E2F‐1 is methylated in tumour cells, and a reduced level of methylation is evident under DNA damage conditions that allow E2F‐1 stabilization and give rise to apoptosis. Significantly, in a subgroup of colorectal cancer, high levels of PRMT5 frequently coincide with low levels of E2F‐1 and reflect a poor clinical outcome. Our results establish that arginine methylation regulates the biological activity of E2F‐1 activity, and raise the possibility that arginine methylation contributes to tumourigenesis by influencing the E2F pathway.
The transcription factor E2F‐1 regulates the cell cycle and apoptosis. E2F‐1 is arginine methylated by PRMT5, leading to degradation and increased cell growth. In colorectal cancer, high levels of PRMT5 correlate with low E2F‐1 and poor clinical outcome.
Electrical tree growth in microsilica-filled epoxy resin Chen, Siyuan; Lv, Zepeng; Carr, James ...
IEEE transactions on dielectrics and electrical insulation,
2020-June, 2020-6-00, 20200601, Letnik:
27, Številka:
3
Journal Article
Recenzirano
Epoxy resin is widely deployed as a high voltage electrical insulation material when compounded with inorganic fillers. However, in the laboratory, the filler prevents visual observation of the ...long-term degradation known as electrical treeing. To date therefore, much laboratory testing has been conducted on unrepresentative unfilled materials. Here, the impact of micro-sized fillers on the treeing phenomenon in an epoxy system has been explored. Sub-micrometre resolution 3D reconstructions of electrical trees are reported from X-ray computed tomography (XCT) using an advanced 'pink beam' synchrotron light source imaging system. The role of filler particles between 1 and 10 μm in size on tree channel propagation is reported. In highly filled materials (30% by weight) a radical change in tree growth behavior is seen, leading to bush tree rather than branch tree growth. The dielectric breakdown time at constant stress was also found to increase as the square root of the filler level. The change in geometry of tree growth may explain the extended life of filled materials in high voltage applications.
Methylation of lysine and arginine residues on histones has long been known to determine both chromatin structure and gene expression. In recent years, the methylation of non‐histone proteins has ...emerged as a prevalent modification which impacts on diverse processes such as cell cycle control, DNA repair, senescence, differentiation, apoptosis and tumourigenesis. Many of these non‐histone targets represent transcription factors, cell signalling molecules and tumour suppressor proteins. Evidence now suggests that the dysregulation of methyltransferases, demethylases and reader proteins is involved in the development of many diseases, including cancer, and several of these proteins represent potential therapeutic targets for small molecule compounds, fuelling a recent surge in chemical inhibitor design. Such molecules will greatly help us to understand the role of methylation in both health and disease.
As a critical target for cyclin‐dependent kinases (Cdks), the retinoblastoma tumour suppressor protein (pRb) controls early cell cycle progression. We report here a new type of regulation that ...influences Cdk recognition and phosphorylation of substrate proteins, mediated through the targeted methylation of a critical lysine residue in the Cdk substrate recognition site. In pRb, lysine (K) 810 represents the essential and conserved basic residue (SPXK) required for cyclin/Cdk recognition and phosphorylation. Methylation of K810 by the methyltransferase Set7/9 impedes binding of Cdk and thereby prevents subsequent phosphorylation of the associated serine (S) residue, retaining pRb in the hypophosphorylated growth‐suppressing state. Methylation of K810 is under DNA damage control, and methylated K810 impacts on phosphorylation at sites throughout the pRb protein. Set7/9 is required for efficient cell cycle arrest, and significantly, a mutant derivative of pRb that cannot be methylated at K810 exhibits compromised cell cycle arrest. Thus, the regulation of phosphorylation by Cdks reflects the combined interplay with methylation events, and more generally the targeted methylation of a lysine residue within a Cdk‐consensus site in pRb represents an important point of control in cell cycle progression.
This study shows that not only lysine methylation, but also modification crosstalk is common to both histone and non‐histone proteins. Inducible methylation of pRb prevents its phosphorylation by cyclin‐dependent kinases, thus contributing to cell cycle arrest upon genotoxic stress.
3D XCT imaging of electrical tree growth in epoxy resin Lv, Zepeng; Chen, Siyuan; Rowland, Simon M. ...
IEEE transactions on dielectrics and electrical insulation,
2020-April, 2020-4-00, 20200401, Letnik:
27, Številka:
2
Journal Article
Recenzirano
This paper reports observations of electrical tree growth by X-ray computed tomography (XCT) in multiple steps. Growth between times of observation has been obtained by subtraction of an image from ...the subsequent one. Partial discharge (PD) signals were also recorded during tree growth. It is determined that not all PDs support tree extension. By comparing the energy released by PD and the vaporization energy of newly grown tree channels, it is found that only the PDs that reach the tree tips can contribute to the growth of tree length. In such cases, the efficiency of energy conversion was very high, whereas PD resulting in increases in tree channel diameter had a much lower conversion efficiency. Nano XCT images reveal many finer branches along the trunk of the main tree and in the front of the main channel tree tips. It seems that those finer branches led to tree growth, but were not directly associated with local PD. The new imaging techniques have shown great value in resolving the relationship between partial discharge activity and electrical tree growth, providing a platform for deeper understanding of the tree growth process, and interpretation of partial discharge measurements.
The retinoblastoma tumor suppressor protein pRb is a key regulator of cell cycle progression and mediator of the DNA damage response. Lysine methylation at K810, which occurs within a critical Cdk ...phosphorylation motif, holds pRb in the hypophosphorylated growth-suppressing state. We show here that methyl K810 is read by the tandem tudor domain containing tumor protein p53 binding protein 1 (53BP1). Structural elucidation of 53BP1 in complex with a methylated K810 pRb peptide emphasized the role of the 53BP1 tandem tudor domain in recognition of the methylated lysine and surrounding residues. Significantly, binding of 53BP1 to methyl K810 occurs on E2 promoter binding factor target genes and allows pRb activity to be effectively integrated with the DNA damage response. Our results widen the repertoire of cellular targets for 53BP1 and suggest a previously unidentified role for 53BP1 in regulating pRb tumor suppressor activity.
The ubiquitin‐like molecule NEDD8 modifies cullin‐RING ubiquitin E3 ligases. NEDD8 has been shown to have a few additional substrates, but the extent to which this modification targets non‐cullins ...and the functional significance of such modifications remain unclear. Here, we demonstrate that the cell‐cycle‐regulating transcription factor E2F‐1 is a substrate for NEDD8 post‐translational modification. NEDDylation results in decreased E2F‐1 stability, lower transcriptional activity and slower cell growth. The lysine residues in E2F‐1 targeted for NEDDylation can also be methylated, pointing to a possible interplay between these modifications. These results identify a new mode of E2F‐1 regulation and highlight the emerging role of NEDD8 in regulating transcription factor stability and function.
This study shows that NEDDylation of E2F‐1 decreases its stability and transcriptional activity, thereby inhibiting E2F‐1‐mediated cell growth. An interplay between E2F‐1 acetylation and NEDDylation is highlighted.
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