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Citation Count: 0
Cytoplasmically localized tRNA-derived fragments inhibit translation in Drosophila S2 cells
(TUBITAK, 2022) Hamid,S.M.; Akgül,B.; Akgül, Bünyamin; Moleküler Biyoloji ve Genetik Bölümü; Moleküler Biyoloji ve Genetik Bölümü
Transfer ribonucleic acids (tRNAs) serve not only as amino acid carriers during translation but also as a template for the biogenesis of short fragments that can regulate gene expression. Despite recent progress in the function of tRNA-derived fragments (tRFs), their intracellular localization, protein partners, and role in regulating translation are not well understood. We used synthetic tRFs to investigate their localization and function in Drosophila S2 cells. Under our experimental setting, all synthetic tRFs tested were localized at distinct sites within the cytoplasm in a similar manner in Drosophila S2 cells. Cytoplasmically-localized tRFs were positioned in close proximity to GW182 and XRN1 proteins. Functionally, tRFs, which slightly suppressed proliferation in S2 cells, inhibited translation without any major shift in the polysome profile. These results suggest that 5’-tRFs are cytoplasmically-localized and regulate gene expression through inhibition of translation in Drosophila. © TÜBİTAK.
Citation Count: 12
Differentially expressed tRNA-derived small RNAs co-sediment primarily with non-polysomal fractions in Drosophila
(MDPI AG, 2017) Akgül, Bünyamin; Yiğit,H.; Coşacak,M.İ.; Akgül,B.
Recent studies point to the existence of poorly characterized small regulatory RNAs generated from mRNAs, rRNAs and tRNAs. To explore the subcellular location of tRNA-derived small RNAs, 0–1 and 7–8 h Drosophila embryos were fractionated on sucrose density gradients. Analysis of 12,553,921 deep-sequencing reads from unfractionated and fractionated Drosophila embryos has revealed that tRFs, which are detected mainly from the 5’ends of tRNAs, co-sediment with the non-polysomal fractions. Interestingly, the expression levels of a subset of tRFs change temporally following thematernal-to-zygotic transition in embryos. We detected non-polysomal association of tRFs in S2 cells as well. Differential tRF expression pattern points to developmental significance at the organismal level. These results suggest that tRFs are associated primarily with the non-polysomal complexes in Drosophila embryos and S2 cells. © 2017 by the authors.
Citation Count: 38
Endogenous miRNA Sponges
(Humana Press Inc., 2022) Akgül, Bünyamin; Akgül,B.
MicroRNAs (miRNAs) are a class of noncoding RNAs of 17–22 nucleotides in length with a critical function in posttranscriptional gene regulation. These master regulators are themselves subject to regulation both transcriptionally and posttranscriptionally. Recently, miRNA function has been shown to be modulated by exogenous RNA molecules that function as miRNA sponges. Interestingly, endogenous transcripts such as transcribed pseudogenes, long noncoding RNAs (lncRNAs), circular RNAs (circRNAs) and mRNAs may serve as natural miRNA sponges. These transcripts, which bind to miRNAs and competitively sequester them away from their targets, are naturally existing endogenous miRNA sponges, called competing endogenous RNAs (ceRNAs). Here we present a historical background of miRNAs, exogenous and endogenous miRNA sponges as well as some examples of endogenous miRNA sponges involved in regulatory mechanisms associated with various diseases, developmental stages, and other cellular processes. © 2022, Springer Science+Business Media, LLC, part of Springer Nature.
Citation Count: 1
Epitranscriptomics Changes the Play: m6A RNA Modifications in Apoptosis
(Springer, 2022) Akçaöz,A.; Akgül, Bünyamin; Akgül,B.
Apoptosis is a form of programmed cell death that is essential for cellular and organismal homeostasis. Any irregularities that disturb the balance between apoptosis and cell survival have severe implications, such as improper development or life-threatening diseases. Thus, it is highly critical to maintain a proper rate of apoptosis throughout development. In fact, several complex transcriptional and posttranscriptional mechanisms exist in eukaryotes to critically regulate the rate of apoptotic processes. Recent studies suggest that not only RNA sequences but also their modifications, such as m6A methylation, play a fundamental role in these transcriptional and posttranscriptional processes. A specific set of proteins, called writer, eraser, and reader of m6A marks, modulate the rate of apoptosis by determining the m6A repertoire and the fate of certain transcripts associated with apoptosis. In this Review, we will cover the dynamic m6A RNA modifications and their impact on modulation of apoptosis. © 2022, Springer Nature Switzerland AG.
Citation Count: 13
Experimental MicroRNA Detection Methods
(Humana Press Inc., 2022) Akgül, Bünyamin; Akgül,B.
MicroRNAs (miRNAs) are considerably small yet highly important riboregulators involved in nearly all cellular processes. Due to their critical roles in posttranscriptional regulation of gene expression, they have the potential to be used as biomarkers in addition to their use as drug targets. Although computational approaches speed up the initial genomewide identification of putative miRNAs, experimental approaches are essential for further validation and functional analyses of differentially expressed miRNAs. Therefore, sensitive, specific, and cost-effective microRNA detection methods are imperative for both individual and multiplex analysis of miRNA expression in different tissues and during different developmental stages. There are a number of well-established miRNA detection methods that can be exploited depending on the comprehensiveness of the study (individual miRNA versus multiplex analysis), the availability of the sample and the location and intracellular concentration of miRNAs. This review aims to highlight not only traditional but also novel strategies that are widely used in experimental identification and quantification of microRNAs. © 2022, Springer Science+Business Media, LLC, part of Springer Nature.
Citation Count: 1
Genomewide m6A Mapping Uncovers Dynamic Changes in the m6A Epitranscriptome of Cisplatin-Treated Apoptotic HeLa Cells
(MDPI, 2022) Alasar,A.A.; Akgül, Bünyamin; Tüncel,Ö.; Gelmez,A.B.; Sağlam,B.; Vatansever,İ.E.; Akgül,B.
Cisplatin (CP), which is a conventional cancer chemotherapeutic drug, induces apoptosis by modulating a diverse array of gene regulatory mechanisms. However, cisplatin-mediated changes in the m6A methylome are unknown. We employed an m6A miCLIP-seq approach to investigate the effect of m6A methylation marks under cisplatin-mediated apoptotic conditions on HeLa cells. Our high-resolution approach revealed numerous m6A marks on 972 target mRNAs with an enrichment on 132 apoptotic mRNAs. We tracked the fate of differentially methylated candidate mRNAs under METTL3 knockdown and cisplatin treatment conditions. Polysome profile analyses revealed perturbations in the translational efficiency of PMAIP1 and PHLDA1 transcripts. Congruently, PMAIP1 amounts were dependent on METTL3. Additionally, cisplatin-mediated apoptosis was sensitized by METTL3 knockdown. These results suggest that apoptotic pathways are modulated by m6A methylation events and that the METTL3–PMAIP1 axis modulates cisplatin-mediated apoptosis in HeLa cells. © 2022 by the authors.
Citation Count: 10
Intracytoplasmic Re-localization of miRISC Complexes
(Frontiers Media Sa, 2018) Akgul, Bunyamin; Erdogan, Ipek; Akgül, Bünyamin
MicroRNAs (miRNAs) are a conserved class of non-coding RNAs of 22 nucleotides that post-transcriptionally regulate gene expression through translational repression and/or mRNA degradation. A great progress has been made regarding miRNA biogenesis and miRNA-mediated gene regulation. Additionally, an ample amount of information exists with respect to the regulation of miRNAs. However, the cytoplasmic localization of miRNAs and its effect on gene regulatory output is still in progress. We provide a current review of the cytoplasmic miRNA localization in metazoans. We then discuss the dynamic changes in the intracytoplasmic localization of miRNAs as a means to regulate their silencing activity. We then conclude our discussion with the potential molecules that could modulate miRNA localization.
Citation Count: 0
Knockdown of death receptor 5 antisense long noncoding RNA and cisplatin treatment modulate similar macromolecular and metabolic changes in HeLa cells
(Tubitak Scientific & Technological Research Council Turkey, 2022) Gurer, Dilek Cansu; Erdogan Vatansever, Ipek; Ceylan, Cagatay; Akgul, Bunyamin; Akgül, Bünyamin
Background/aim: Despite great progress in complex gene regulatory mechanisms in the dynamic tumor microenvironment, the potential contribution of long noncoding RNAs (lncRNAs) to cancer cell metabolism is poorly understood. Death receptor 5 antisense (DR5-AS) is a cisplatin inducible lncRNA whose knockdown modulates cell morphology. However, its effect on cell metabolism is unknown. The aim of this study is to examine metabolic changes modulated by cisplatin and DR5-AS lncRNA in HeLa cells.Materials and methods: We used cisplatin as a universal cancer therapeutic drug to modulate metabolic changes in HeLa cervix cancer cells. We then examined the extent of metabolic changes by Fourier transform infrared spectroscopy (FTIR). We also performed transcriptomics analyses by generating new RNA-seq data with total RNAs isolated from cisplatin-treated HeLa cells. Then, we compared cisplatin-mediated transcriptomics and macromolecular changes with those mediated by DR5-AS knockdown.Results: Cisplatin treatment caused changes in the unsaturated fatty acid and lipid-to-protein ratios and the glycogen content. These observations in altered cellular metabolism were supported by transcriptomics analyses. FTIR spectroscopy analyses have revealed that DR5-AS knockdown causes a 20.9% elevation in the lipid/protein ratio and a 76.6% decrease in lipid peroxidation. Furthermore, we detected a 3.42% increase in the chain length of the aliphatic lipids, a higher content of RNA, and a lower amount of glycogen indicating relatively lower metabolic activity in the DR5-AS knockdown HeLa cells. Interestingly, we observed a similar gene expression pattern under cisplatin treatment and DR5-AS knockdown HeLa cells. Conclusion: These results suggest that DR5-AS lncRNA appears to account for a fraction of cisplatin-mediated macromolecular and metabolic changes in HeLa cervix cancer cells.
Citation Count: 0
Knockdown of death receptor 5 antisense long noncoding RNA and cisplatin treatment modulate similar macromolecular and metabolic changes in HeLa cells
(TUBITAK, 2022) Gürer,D.C.; Akgül, Bünyamin; Erdoğan Vatansever,İ.; Ceylan,Ç.; Akgül,B.
Background/aim: Despite great progress in complex gene regulatory mechanisms in the dynamic tumor microenvironment, the potential contribution of long noncoding RNAs (lncRNAs) to cancer cell metabolism is poorly understood. Death receptor 5 antisense (DR5-AS) is a cisplatin inducible lncRNA whose knockdown modulates cell morphology. However, its effect on cell metabolism is unknown. The aim of this study is to examine metabolic changes modulated by cisplatin and DR5-AS lncRNA in HeLa cells. Materials and methods: We used cisplatin as a universal cancer therapeutic drug to modulate metabolic changes in HeLa cervix cancer cells. We then examined the extent of metabolic changes by Fourier transform infrared spectroscopy (FTIR). We also performed transcriptomics analyses by generating new RNA-seq data with total RNAs isolated from cisplatin-treated HeLa cells. Then, we compared cisplatin-mediated transcriptomics and macromolecular changes with those mediated by DR5-AS knockdown. Results: Cisplatin treatment caused changes in the unsaturated fatty acid and lipid-to-protein ratios and the glycogen content. These observations in altered cellular metabolism were supported by transcriptomics analyses. FTIR spectroscopy analyses have revealed that DR5-AS knockdown causes a 20.9% elevation in the lipid/protein ratio and a 76.6% decrease in lipid peroxidation. Furthermore, we detected a 3.42% increase in the chain length of the aliphatic lipids, a higher content of RNA, and a lower amount of glycogen indicating relatively lower metabolic activity in the DR5-AS knockdown HeLa cells. Interestingly, we observed a similar gene expression pattern under cisplatin treatment and DR5-AS knockdown HeLa cells. Conclusion: These results suggest that DR5-AS lncRNA appears to account for a fraction of cisplatin-mediated macromolecular ametabolic changes in HeLa cervix cancer cells. © TÜBİTAK.
Citation Count: 5
Long Noncoding RNAs in Human Cancer and Apoptosis
(Bentham Science Publ Ltd, 2023) Erdogan, Ipek; Sweef, Osama; Akgul, Bunyamin; Akgül, Bünyamin
Genome annotations have uncovered the production of at least one transcript from nearly all loci in the genome at some given time throughout the development. Surprisingly, many of these transcripts do not code for proteins and are relatively long in size, thus called long noncoding RNAs (lncRNAs). Next- and third-generation sequencing technologies have amassed numerous lncRNAs expressed under different phenotypic conditions, yet many remain to be functionally characterized. LncRNAs regulate gene expression by functioning as scaffold, decoy, signaling, and guide molecules both at the transcriptional and post-transcriptional levels, interacting with different types of macromolecules, such as proteins, DNA, and RNA. Here, we review the potential regulatory role of lncRNAs in apoptosis and cancer as some of these lncRNAs may have the diagnostic and therapeutic potential in cancer.
Citation Count: 3
Noncoding RNAs in apoptosis: identification and function
(Tubitak Scientific & Technological Research Council Turkey, 2022) Tuncel, Ozge; Kara, Merve; Yaylak, Bilge; Erdogan, Ipek; Akgul, Bunyamin; Akgül, Bünyamin
Apoptosis is a vital cellular process that is critical for the maintenance of homeostasis in health and disease. The derailment of apoptotic mechanisms has severe consequences such as abnormal development, cancer, and neurodegenerative diseases. Thus, there exist complex regulatory mechanisms in eukaryotes to preserve the balance between cell growth and cell death. Initially, protein coding genes were prioritized in the search for such regulatory macromolecules involved in the regulation of apoptosis. However, recent genome annotations and transcriptomics studies have uncovered a plethora of regulatory noncoding RNAs that have the ability to modulate not only apoptosis but also many other biochemical processes in eukaryotes. In this review article, we will cover a brief summary of apoptosis and detection methods followed by an extensive discussion on microRNAs, circular RNAs, and long noncoding RNAs in apoptosis.
Citation Count: 1
Noncoding RNAs: A New Layer of Functional RNAs
(Bentham Science Publ Ltd, 2023) Gurer, Dilek Cansu; Akgul, Bunyamin; Akgül, Bünyamin
The conventional central dogma of molecular biology dictates that the genetic information contained within deoxyribonucleic acid (DNA) is passed onto messenger ribonucleic acids (mRNAs), which are then used as templates to synthesize proteins. Although these types of protein-coding genes have been historically prioritized in typical phenotype-genotype studies with a parallel disregard to the rest of the genome, the completion of genome projects has unveiled a surprising layer of genetic information that can play critical roles in cellular processes without coding for proteins. These types of genes are called noncoding genes as they do not code for proteins. Noncoding genes come in different sizes and shapes, and they are just as versatile in carrying out cellular biochemical processes as proteins. In this review, we cover a comprehensive review of housekeeping and regulatory noncoding genes and their mode of action.
Citation Count: 6
Re-arrangements in the cytoplasmic distribution of small RNAs following the maternal-to-zygotic transition in Drosophila embryos
(MDPI AG, 2018) Akgül, Bünyamin; Yiğit,H.; Kizil,C.; Akgül,B.
Small ribonucleic acids (RNAs) are known to regulate gene expression during early development. However, the dynamics of interaction between small RNAs and polysomes during this process is largely unknown. To investigate this phenomenon, 0-1 h and 7-8 h Drosophila melanogaster embryos were fractionated on sucrose density gradients into four fractions based on A254 reading (1) translationally inactive messenger ribonucleoprotein (mRNP), (2) 60S, (3) monosome, and (4) polysome. Comparative analysis of deep-sequencing reads from fractionated and un-fractionated 0-1 h and 7-8 h embryos revealed development-specific co-sedimentation pattern of small RNAs with the cellular translation machinery. Although most micro RNAs (miRNAs) did not have a specific preference for any state of the translational machinery, we detected fraction-specific enrichment of a few miRNAs such as dme-miR-1-3p, -184-3p, 5-5p and 263-5p. More interestingly, we observed changes in the subcellular location of a subset of miRNAs in fractionated embryos despite no measurable difference in their amount in unfractionated embryos. Transposon-derived endo small interfering RNAs (siRNAs) were over-expressed in 7-8 h embryos and associated mainly with the mRNP fraction. In contrast, transposon-derived PIWI-interacting RNAs (piRNA), which were more abundant in 0-1 h embryos, co-sedimented primarily with the polysome fractions. These results suggest that there appears to be a complex interplay among the small RNAs with respect to their polysome-cosedimentation pattern during early development in Drosophila melanogaster. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.
Citation Count: 3
Small RNA data set that includes tRNA-derived fragments from Jurkat cells treated with camptothecin
(Elsevier Science Bv, 2018) Cosacak, Mehmet Ilyas; Erdogan, Ipek; Nalbant, Ayten; Akgul, Bunyamin; Akgül, Bünyamin
In this article, we report a small RNA data set obtained from human T cell acute leukemia Jurkat cells, which were treated with the universal apoptotic agent camptothecin. Based on the Annexin-V labeling pattern, we sorted two Jurkat subpopulations in treated cells: one that is sensitive to the drug and the other being relatively more resistant. We report new original data that include the frequency of tRNA-derived fragments (tRF) in drug-sensitive and resistant cells. We also present partially analyzed data to show the origin of reads on tRNAs as well as the borders of the fragments. We believe that this data can benefit the science community working in the field of tRF and/or apoptosis. (C) 2018 The Authors. Published by Elsevier Inc.
Citation Count: 8
Transcriptomics analysis of circular RNAs differentially expressed in apoptotic HeLa cells
(Frontiers Media S.A., 2019) Yaylak,B.; Erdogan,I.; Akgul,B.; Akgül, Bünyamin
Apoptosis is a form of regulated cell death that plays a critical role in survival and developmental homeostasis. There are numerous reports on regulation of apoptosis by protein-coding genes as well as small non-coding RNAs, such as microRNAs. However, there is no comprehensive investigation of circular RNAs (circRNA) that are differentially expressed under apoptotic conditions. We have performed a transcriptomics study in which we first triggered apoptosis in HeLa cells through treatment with four different agents, namely cisplatin, doxorubicin, TNF-á and anti-Fas mAb. Total RNAs isolated from control as well as treated cells were treated with RNAse R to eliminate the linear RNAs. The remaining RNAs were then subjected to deep-sequencing to identify differentially expressed circRNAs. Interestingly, some of the dys-regulated circRNAs were found to originate from protein-coding genes well-documented to regulate apoptosis. A number of candidate circRNAs were validated with qPCR with or without RNAse R treatment as well. We then took advantage of bioinformatics tools to investigate the coding potential of differentially expressed RNAs. Additionally, we examined the candidate circRNAs for the putative miRNA-binding sites and their putative target mRNAs. Our analyses point to a potential for circRNA-mediated sponging of miRNAs known to regulate apoptosis. In conclusion, this is the first transcriptomics study that provides a complete circRNA profile of apoptotic cells that might shed light onto the potential role of circRNAs in apoptosis. © 2019 Frontiers Media S.A. All Rights Reserved.
Citation Count: 5
Transcriptomics Profiling Identifies Cisplatin-Inducible Death Receptor 5 Antisense Long Non-coding RNA as a Modulator of Proliferation and Metastasis in HeLa Cells
(Frontiers Media Sa, 2021) Gurer, Dilek Cansu; Erdogan, Ipek; Ahmadov, Ulvi; Basol, Merve; Sweef, Osama; Cakan-Akdogan, Gulcin; Akgul, Bunyamin; Akgül, Bünyamin
Cisplatin is a well-known cancer chemotherapeutic agent but how extensively long non-coding RNA (lncRNA) expression is modulated by cisplatin is unknown. It is imperative to employ a comprehensive approach to obtain a better account of cisplatin-mediated changes in the expression of lncRNAs. In this study, we used a transcriptomics approach to profile lncRNAs in cisplatin-treated HeLa cells, which resulted in identification of 10,214 differentially expressed lncRNAs, of which 2,500 were antisense lncRNAs. For functional analyses, we knocked down one of the cisplatin inducible lncRNAs, death receptor 5 antisense (DR5-AS) lncRNA, which resulted in a morphological change in HeLa cell shape without inducing any cell death. A second round of transcriptomics-based profiling revealed differential expression of genes associated with immune system, motility and cell cycle in DR5-AS knockdown HeLa cells. Cellular analyses showed that DR5-AS reduced cell proliferation and caused a cell cycle arrest at S and G2/M phases. Moreover, DR5-AS knockdown reduced the invasive capacity of HeLa cells in zebrafish xenograft model. These results suggest that cisplatin-mediated pleiotropic effects, such as reduction in cell proliferation, metastasis and cell cycle arrest, may be mediated by lncRNAs.

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