The HERV-K (HML-2) viruses are the youngest of the human endogenous retroviruses. They are present as several almost complete proviral copies and numerous fragments in the human genome. Many HERV-K ...proviruses express a regulatory protein Rec, which binds to an element present in HERV-K mRNAs called the RcRE. This interaction is necessary for the nucleo-cytoplasmic export and expression of HERV-K mRNAs that retain introns and plays a role analogous to that of Rev and the RRE in HIV replication. There are over 900 HERV-K RcREs distributed throughout the human genome. Thus, it was of interest to determine if Rev could functionally interact with selected RcRE elements that map either to HERV-K proviruses or human gene regions. This interaction would have the potential to alter the expression of both HERV-K mRNAs and cellular mRNAs during HIV-1 infection.
In this study we employed a combination of RNAseq, bioinformatics and cell-based functional assays. Potential RcREs were identified through a number of bioinformatic approaches. They were then tested for their ability to promote export and translation of a reporter mRNA with a retained intron in conjunction with Rev or Rec. Some of the selected elements functioned well with either Rev, Rec or both, whereas some showed little or no function. Rev function on individual RcREs varied and was also dependent on the Rev sequence. We also performed RNAseq on total and cytoplasmic RNA isolated from SupT1 cells expressing HIV Rev, with or without Tat, or HERV-K Rec. Proviral mRNA from three HERV-K loci (4p16.1b, 22q11.23 and most significantly 3q12.3) accumulated in the cytoplasm in the presence of Rev or Tat and Rev, but not Rec. Consistent with this, the 3' RcRE from 3q12.3 functioned well with HIV-Rev in our reporter assay. In contrast, this RcRE showed little or no function with Rec.
The HIV Rev protein can functionally interact with many RcREs present in the human genome, depending on the RcRE sequence, as well as the Rev sequence. This leads to export of some of the HERV-K proviral mRNAs and also has the potential to change the expression of non-viral genes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Transcriptome studies on eukaryotic cells have revealed an unexpected abundance and diversity of noncoding RNAs synthesized by RNA polymerase II (Pol II), some of which influence the expression of ...protein-coding genes. Yet, much less is known about biogenesis of Pol II non-coding RNA than mRNAs. In the budding yeast Saccharomyces cerevisiae, initiation of non-coding transcripts by Pol II appears to be similar to that of mRNAs, but a distinct pathway is utilized for termination of most non-coding RNAs: the Sen1-dependent or "NNS" pathway. Here, we examine the effect on the S. cerevisiae transcriptome of conditional mutations in the genes encoding six different essential proteins that influence Sen1-dependent termination: Sen1, Nrd1, Nab3, Ssu72, Rpb11, and Hrp1. We observe surprisingly diverse effects on transcript abundance for the different proteins that cannot be explained simply by differing severity of the mutations. Rather, we infer from our results that termination of Pol II transcription of non-coding RNA genes is subject to complex combinatorial control that likely involves proteins beyond those studied here. Furthermore, we identify new targets and functions of Sen1-dependent termination, including a role in repression of meiotic genes in vegetative cells. In combination with other recent whole-genome studies on termination of non-coding RNAs, our results provide promising directions for further investigation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background: We have identified, in melanomas, a set of genes encoding proteins that mediate mechanical barrier function in normal skin (barrier molecule genes, BMGs) and whose overexpression is ...associated with decreased immune signatures and shorter patient survival. The most overexpressed of these, filaggrin (FLG), is expressed on chromosome 1q21.3, which also encodes genes of the epidermal differentiation complex (EDC). EDC genes may be regulated by the transcription factors (TFs) AHR and ARNT. We hypothesized that ARNT-related genes would be expressed concordantly with BMG and EDC genes, inversely associated with immune signatures, and enhanced by 1q21.3 copy gain.
Methods: Gene expression data from human melanomas in the Cancer Genome Atlas (TCGA), and a validation GEO dataset were evaluated, with copy number profiles from TCGA. Expression of Th1 immune genes and BMG/EDCs at 1q21.3 was visualized using clustered copy number and mRNA profiles. Associations of clusters and 1q21.3 copy number with patient survival and mRNA expression were assessed using Kaplan Meier curves, log-rank tests, and Wilcoxon rank sum tests.
Results: BMGs are concordantly expressed with EDC genes. Clustering divided tumors into 4 categories: (1) Immune
HI
, (2) BMG/EDC
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, (3) ARNT
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, (4) Mixed. Both ARNT
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and BMG/EDC
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tumors had low immune signatures and significantly shortened survival. KLF4 and FOXF2 are putative TFs that may regulate these genes.
Conclusions: ARNT
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tumors may represent another subset of tumors, in addition to BMG/EDC
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tumors, with barriers to immune infiltrates, likely with different mechanisms. These genes have prognostic significance and may be relevant targets for future therapy.
Spinocerebellar ataxia type 7 (SCA7) is an autosomal-dominant neurodegenerative disorder that results from polyglutamine expansion of the ataxin-7 (ATXN7) protein. Remarkably, although mutant ATXN7 ...is expressed throughout the body, pathology is restricted primarily to the cerebellum and retina. One major goal has been to identify factors that contribute to the tissue specificity of SCA7. Here we describe the development and use of a human astrocyte cell culture model to identify reelin, a factor intimately involved in the development and maintenance of Purkinje cells and the cerebellum as a whole, as an ATXN7 target gene. We found that polyglutamine expansion decreased ATXN7 occupancy, which correlated with increased levels of histone H2B monoubiquitination, at the reelin promoter. Treatment with trichostatin A, but not other histone deacetylase inhibitors, partially restored reelin transcription and promoted the accumulation of mutant ATXN7 into nuclear inclusions. Our findings suggest that reelin could be a previously unknown factor involved in the tissue specificity of SCA7 and that trichostatin A may ameliorate deleterious effects of the mutant ATXN7 protein by promoting its sequestration away from promoters into nuclear inclusions.
Targeted therapies have often given disappointing results when used as single agents in solid tumors, suggesting the importance of devising rational combinations of targeted drugs. We hypothesized ...that construction of such combinations could be guided by identification of growth and survival pathways whose activity or expression become upregulated in response to single-agent drug treatment. We mapped alterations in signaling pathways assessed by gene array and protein phosphorylation to identify compensatory signal transduction pathways in prostate cancer xenografts treated with a MAP/ERK kinase (MEK) inhibitor PD325901. In addition to numerous components of the extracellular signal-regulated kinase (ERK) signaling pathway, components of the IKK, hedgehog, and phosphoinositide 3-kinase/Akt/mTOR pathways were upregulated following treatment with PD325901. Combinations of PD325901 with inhibitors of any one of these upregulated pathways provided synergistically greater growth inhibition of in vitro cell growth and survival than the individual drugs alone. Thus, the identification of compensatory signal transduction pathways paves the way for rational combinatorial therapies for the effective treatment of prostate cancer.
Numerous studies have identified prognostic genes in individual cancers, but a thorough pan-cancer analysis has not been performed. In addition, previous studies have mostly used microarray data ...instead of RNA-SEQ, and have not published comprehensive lists of associations with survival. Using recently available RNA-SEQ and clinical data from The Cancer Genome Atlas for 6,495 patients, we have investigated every annotated and expressed gene's association with survival across 16 cancer types. The most statistically significant harmful and protective genes were not shared across cancers, but were enriched in distinct gene sets which were shared across certain groups of cancers. These groups of cancers were independently recapitulated by both unsupervised clustering of Cox coefficients (a measure of association with survival) for individual genes, and for gene programs. This analysis has revealed unappreciated commonalities among cancers which may provide insights into cancer pathogenesis and rationales for co-opting treatments between cancers.
Abstract
Motivation
The rapid advance in single-cell RNA sequencing (scRNA-seq) technology over the past decade has provided a rich resource of gene expression profiles of single cells measured on ...patients, facilitating the study of many biological questions at the single-cell level. One intriguing research is to study the single cells which play critical roles in the phenotypes of patients, which has the potential to identify those cells and genes driving the disease phenotypes. To this end, deep learning models are expected to well encode the single-cell information and achieve precise prediction of patients’ phenotypes using scRNA-seq data. However, we are facing critical challenges in designing deep learning models for classifying patient samples due to (i) the samples collected in the same dataset contain a variable number of cells—some samples might only have hundreds of cells sequenced while others could have thousands of cells, and (ii) the number of samples available is typically small and the expression profile of each cell is noisy and extremely high-dimensional. Moreover, the black-box nature of existing deep learning models makes it difficult for the researchers to interpret the models and extract useful knowledge from them.
Results
We propose a prototype-based and cell-informed model for patient phenotype classification, termed ProtoCell4P, that can alleviate problems of the sample scarcity and the diverse number of cells by leveraging the cell knowledge with representatives of cells (called prototypes), and precisely classify the patients by adaptively incorporating information from different cells. Moreover, this classification process can be explicitly interpreted by identifying the key cells for decision making and by further summarizing the knowledge of cell types to unravel the biological nature of the classification. Our approach is explainable at the single-cell resolution which can identify the key cells in each patient’s classification. The experimental results demonstrate that our proposed method can effectively deal with patient classifications using single-cell data and outperforms the existing approaches. Furthermore, our approach is able to uncover the association between cell types and biological classes of interest from a data-driven perspective.
Availability and implementation
https://github.com/Teddy-XiongGZ/ProtoCell4P.
Fifty percent of cutaneous melanomas are driven by activated BRAFV600E, but tumors treated with RAF inhibitors, even when they respond dramatically, rapidly adapt and develop resistance. Thus, there ...is a pressing need to identify the major mechanisms of intrinsic and adaptive resistance and develop drug combinations that target these resistance mechanisms. In a combinatorial drug screen on a panel of 12 treatment-naïve BRAFV600E mutant melanoma cell lines of varying levels of resistance to mitogen-activated protein kinase (MAPK) pathway inhibition, we identified the combination of PLX4720, a targeted inhibitor of mutated BRaf, and lapatinib, an inhibitor of the ErbB family of receptor tyrosine kinases, as synergistically cytotoxic in the subset of cell lines that displayed the most resistance to PLX4720. To identify potential mechanisms of resistance to PLX4720 treatment and synergy with lapatinib treatment, we performed a multi-platform functional genomics analysis to profile the genome as well as the transcriptional and proteomic responses of these cell lines to treatment with PLX4720. We found modest levels of resistance correlated with the zygosity of the BRAF V600E allele and receptor tyrosine kinase (RTK) mutational status. Layered over base-line resistance was substantial upregulation of many ErbB pathway genes in response to BRaf inhibition, thus generating the vulnerability to combination with lapatinib. The transcriptional responses of ErbB pathway genes are associated with a number of transcription factors, including ETS2 and its associated cofactors that represent a convergent regulatory mechanism conferring synergistic drug susceptibility in the context of diverse mutational landscapes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Human Endogenous Retroviruses are a class of genomic elements that are the result of ancient retroviral infection of the human germline. Many are biologically active elements that have been ...implicated in multiple diseases including cancer. The most recent class to invade the human genome is the HERV-K(HML-2) (HERV-K) family. Approximately 90 HERV-K proviruses and many smaller elements have been identified to date in the human genome. Additional proviruses are continually being discovered with the rapid advancement of deep-sequencing and long-read sequencing technologies. HERV-K proviruses are poorly annotated in human transcriptome databases making their analysis in RNA-seq data difficult. To enable analysis, we compiled the sequences of 91 HERV-K proviruses identified in NCBI GenBank (ID JN675007-JN675097) and created a proviral alignment tool for visualizing RNA-seq reads aligned across individual proviruses. This allowed us to analyse publicly available RNA-seq data from 10 hepatoblastoma samples and 3 normal liver controls (GEO Accession ID: GSE89775). This data report includes the raw FASTA sequence files of the HERV-K proviruses from NCBI, a differential gene expression list between hepatoblastoma samples, and genomic alignment figures from 5 HERV-K proviruses identified as differentially expressed in the companion research article “Upregulation of Human Endogenous Retrovirus-K (HML-2) mRNAs in hepatoblastoma: Identification of potential new immunotherapeutic targets and biomarkers 1. The data provided here are available for other research groups interested in evaluating individual HERV-K proviral expression using RNA-seq data. Furthermore, the data analysis is highly flexible and will accommodate the addition of other HERV-K proviruses.
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