The Role of Telomeres and Telomere-associated Proteins as Components of Interactome in Cell-signaling Pathways

Telomeres represent ends of all eukaryotic chromosomes and serve specialized biological role in maintaining genomic integrity by preventing end fusions and degradation. Various protein complexes associate with telomeres to either protect them from DNA damage machinery or maintain telomere length homeostasis. These protein complex subunits cross talk with a variety of cell-signaling components to either maintain telomere integrity or perform other functions, which are either dependent or independent of telomeres and/or their telomeric role. Mutations in these protein components lead to the development of various human diseases, such as age-related disorders, which occur mainly due to telomere dysfunction or cancer development due to telomerase reactivation. This chapter focuses on the structural and functional aspects of telomeric proteins and their importance in human diseases

Cancer clocks in tumourigenesis : the p53 pathway and beyond

Circadian rhythms regulate a vast array of physiological and cellular processes, as well as the hormonal milieu, to keep our cells synchronised to the light-dark cycle. Epidemiologic studies have implicated circadian disruption in the development of breast and other cancers, and numerous clock genes are dysregulated in human tumours. Here we review the evidence that circadian rhythms, when altered at the molecular level, influence cancer growth. We also note some common pitfalls in circadian-cancer research and how they might be avoided to maximise comparable results and minimise misleading data. Studies of circadian gene mutant mice, and human cancer models in vitro and in vivo, demonstrate that clock genes can impact tumourigenesis. Clock genes influence important cancer related pathways, ranging from p53-mediated apoptosis to cell cycle progression. Confusingly, clock dysfunction can be both pro- or anti- tumourigenic in a model and cell type specific manner. Due to this duality, there is no canonical mechanism for clock interaction with tumourigenic pathways. To understand the role of the circadian clock in patients’ tumours requires analysis of the molecular clock status compared to healthy tissue. Novel mathematical approaches are under development, but this remains largely aspirational, and is hampered by a lack of temporal information in publicly available datasets. Current evidence broadly supports the notion that the circadian clock is important for cancer biology. More work is necessary to develop an overarching model of this connection. Future studies would do well to analyse the clock network in addition to alterations in single clock genes

NAIL: An evolutionarily conserved lncRNA essential for licensing coordinated activation of p38 and NFκB in colitis

Akıncılar SC, Wu L, NG QF, et al., NAIL: an evolutionarily conserved lncRNA essential for licensing coordinated activation of p38 and NFκB in colitis. Gut Published Online First: 25 November 2020. doi: 10.1136/gutjnl-2020-32298

Chromatin interaction neural network (ChINN): a machine learning-based method for predicting chromatin interactions from DNA sequences.

Chromatin interactions play important roles in regulating gene expression. However, the availability of genome-wide chromatin interaction data is limited. We develop a computational method, chromatin interaction neural network (ChINN), to predict chromatin interactions between open chromatin regions using only DNA sequences. ChINN predicts CTCF- and RNA polymerase II-associated and Hi-C chromatin interactions. ChINN shows good across-sample performances and captures various sequence features for chromatin interaction prediction. We apply ChINN to 6 chronic lymphocytic leukemia (CLL) patient samples and a published cohort of 84 CLL open chromatin samples. Our results demonstrate extensive heterogeneity in chromatin interactions among CLL patient samples

Matriptase activation of gq drives epithelial disruption and inflammation via RSK and DUOX

Epithelial tissues are primed to respond to insults by activating epithelial cell motility and rapid inflammation. Such responses are also elicited upon overexpression of the membrane-bound protease, Matriptase, or mutation of its inhibitor, Hai1. Unrestricted Matriptase activity also predisposes to carcinoma. How Matriptase leads to these cellular outcomes is unknown. We demonstrate that zebrafish hai1a mutants show increased H2O2, NfκB signalling, and IP3R -mediated calcium flashes, and that these promote inflammation, but do not generate epithelial cell motility. In contrast, inhibition of the Gq subunit in hai1a mutants rescues both the inflammation and epithelial phenotypes, with the latter recapitulated by the DAG analogue, PMA. We demonstrate that hai1a has elevated MAPK pathway activity, inhibition of which rescues the epidermal defects. Finally, we identify RSK kinases as MAPK targets disrupting adherens junctions in hai1a mutants. Our work maps novel signalling cascades mediating the potent effects of Matriptase on epithelia, with implications for tissue damage response and carcinoma progression

Systematic Identification of Factors for Provirus Silencing in Embryonic Stem Cells

Embryonic stem cells (ESCs) repress the expression of exogenous proviruses and endogenous retroviruses (ERVs). Here, we systematically dissected the cellular factors involved in provirus repression in embryonic carcinomas (ECs) and ESCs by a genome-wide siRNA screen. Histone chaperones (Chaf1a/b), sumoylation factors (Sumo2/Ube2i/Sae1/Uba2/Senp6), and chromatin modifiers (Trim28/Eset/Atf7ip) are key determinants that establish provirus silencing. RNA-seq analysis uncovered the roles of Chaf1a/b and sumoylation modifiers in the repression of ERVs. ChIP-seq analysis demonstrates direct recruitment of Chaf1a and Sumo2 to ERVs. Chaf1a reinforces transcriptional repression via its interaction with members of the NuRD complex (Kdm1a, Hdac1/2) and Eset, while Sumo2 orchestrates the provirus repressive function of the canonical Zfp809/Trim28/Eset machinery by sumoylation of Trim28. Our study reports a genome-wide atlas of functional nodes that mediate proviral silencing in ESCs and illuminates the comprehensive, interconnected, and multi-layered genetic and epigenetic mechanisms by which ESCs repress retroviruses within the genome

Rap1 regulates hematopoietic stem cell survival and affects oncogenesis and response to chemotherapy

Khattar, E., Maung, K.Z.Y., Chew, C.L. et al. Rap1 regulates hematopoietic stem cell survival and affects oncogenesis and response to chemotherapy. Nat Commun 10, 5349 (2019). https://doi.org/10.1038/s41467-019-13082-

Rho protein GTPases and their interactions with NFκB: crossroads of inflammation and matrix biology

The RhoGTPases, with RhoA, Cdc42 and Rac being major members, are a group of key ubiquitous proteins present in all eukaryotic organisms that subserve such important functions as cell migration, adhesion and differentiation. The NFκB (nuclear factor κB) is a family of constitutive and inducible transcription factors that through their diverse target genes, play a major role in processes such as cytokine expression, stress regulation, cell division and transformation. Research over the past decade has uncovered new molecular links between the RhoGTPases and the NFκB pathway, with the RhoGTPases playing a positive or negative regulatory role on NFκB activation depending on the context. The RhoA–NFκB interaction has been shown to be important in cytokine-activated NFκB processes, such as those induced by TNFα (tumour necrosis factor α). On the other hand, Rac is important for activating the NFκB response downstream of integrin activation, such as after phagocytosis. Specific residues of Rac1 are important for triggering NFκB activation, and mutations do obliterate this response. Other upstream triggers of the RhoGTPase–NFκB interactions include the suppressive p120 catenin, with implications for skin inflammation. The networks described here are not only important areas for further research, but are also significant for discovery of targets for translational medicine

Multifaceted link between cancer and inflammation

10.1042/BSR20100136Bioscience Reports3211-15BRPT