Browsing by Subject "RNAi"

Now showing 1 - 4 of 4

Open Access
Effects of Cholinergic Receptor Nicotinic Alpha 5 (CHRNA5) RNAi on apoptosis, DNA damage response, drug sensitivity, and HSA-MIR-495-3P overexpression in breast cancer
(2018-12) Köker, Şahika Cıngır
Cholinergic Receptor Nicotinic Alpha 5 (CHRNA5) is associated with nicotine addiction and it has an important role in the prognosis of lung cancer. Despite its important cellular functions, its role in breast cancer remains to be elucidated. In this thesis, I aimed to identify the alterations in the important cancer signaling pathways occurring upon CHRNA5 depletion. Drug resistance is one of the major obstacles in breast cancer therapy. Heterogeneous nature of breast cancer necessitates identification of more biomarkers which aid in precise diagnosis and hence development of proper treatment options. In this study, by using more than one cell line which is representative of different subtypes of breast cancer, I showed the alterations occurred in cancer signaling pathways such as cell cycle and apoptosis upon CHRNA5 depletion, which could serve as a novel biomarker in breast cancer subtyping. Depending on mutation status of TP53, which is the gatekeeper protein during G1/S checkpoint, CHRNA5 depletion mostly exerted its effects over decreasing the levels of total CHEK1 and pCHEK1 (S345) which significantly altered the response of MCF7 cells to topoisomerase inhibitors in terms of enhanced drug sensitivity. Increases in apoptotic markers, such as BAX/BCL2 ratio along with increased FAS levels, further confirmed that this sensitization of MCF7 cells upon CHRNA5 depletion might have ended with apoptosis. So far in the literature, there is no study examining the regulation of CHRNA5 by small endogenous molecules such as miRNAs. Due to the predictive binding sites in 3’UTR of CHRNA5 and the importance of participating in tamoxifen resistance in breast cancer; I also examined the interplay between miR-15a family and CHRNA5 in MCF7 cells. I showed significant decrease in CHRNA5 levels upon using miR-15a mimic while demonstrating similar activity of miR-15a family mimics with CHRNA5 depletion using RT-qPCR. Another important implication of CHRNA5 depletion in MCF7 cells was the global change in miRNA expression prolife which was verified with independent microRNA arrays. Based on these in silico results, hsa-miR-495-3p appeared as the most downregulated miRNA which is known as a tumor suppressor miRNA. As stated in the literature, the role of miR-495 differs depending on the tumor type. Therefore, I tried to restore its expression by mimicking along with CHRNA5 depletion. The transcriptomic changes observed with CHRNA5 depletion was boosted with the restoration of miR-495 levels.
Open Access
Effects of depletion of CHRNA5 and/or TP53, and transient and stable overexpression of wildtype or mutant TP53 on expression of DLK1-MEG3 locus in MCF7 cells
(2022-09) Arıcı, Burçin İrem
The expression of CHRNA5 has a prominent role in lung cancer and nicotine addiction. Besides, depletion of CHRNA5 has been identified as being tumour suppressive in breast cancer. Moreover, CHRNA5 depletion causes increases in CDKN1A expression, downregulates the 14q32.31 miRNAs and decreases DLK1 expression. This thesis examined the effects of CHRNA5 and/or TP53 downregulation, as well as TP53 overexpression, on the expression of the DLK1-DIO3 region. My findings demonstrated that CHRNA5 depletion decreased the expression of the protein-coding DLK1 and the non-protein coding MEG3 genes in this locus in the presence or absence of TP53. Since these two genes have a vital role in tumour suppression and tumorigenesis, this provided more evidence for the importance of CHRNA5 in the modulation of expression in this locus in breast cancer. Since there is a relation between CHRNA5 and TP53 induction, the expression of one of the main TP53 regulators, MDM2, was also studied. Accordingly, it was found that combining CHRNA5 depletion with TP53 depletion caused a significant decrease in expression in both the MDM2 and MDM2 sequestering elements, PDLIM7 and CDH18. Additionally, the effects of both wild-type and mutant TP53 expression levels on DLK1-MEG3 locus and CHRNA5 were investigated in stable MCF7 breast cancer cells that we have generated. I have found that even if CHRNA5 depletion induced p53 expression, TP53 overexpression did not have CHRNA5-inducing effects regardless of the functionality of TP53. However, wild-type TP53 overexpressing MCF7 cells behaved differently than mutant TP53 overexpressing cells in their DLK1 expression levels. Future research should clarify the effects of CHRNA5 depletion on DLK1-MEG3 region for a given TP53 mutation status.
Open Access
PACT establishes a posttranscriptional brake on mitochondrial biogenesis by promoting the maturation of miR-181c
(American Society for Biochemistry and Molecular Biology Inc., 2022-07) Doğan, Aslı Ekin; Hamid, Syed M.; Yıldırım, Aslı Dilber; Yıldırım, Zehra; Sen, Ganes; Riera, Celine E.; Gottlieb, Roberta A.; Erbay, Ebru
The double-stranded RNA-dependent protein kinase activating protein (PACT), an RNA-binding protein that is part of the RNA-induced silencing complex, plays a key role in miR-mediated translational repression. Previous studies showed that PACT regulates the expression of various miRs, selects the miR strand to be loaded onto RNA-induced silencing complex, and determines proper miR length. Apart from PACT's role in mediating the antiviral response in immune cells, what PACT does in other cell types is unknown. Strikingly, it has also been shown that cold exposure leads to marked downregulation of PACT protein in mouse brown adipose tissue (BAT), where mitochondrial biogenesis and metabolism play a central role. Here, we show that PACT establishes a posttranscriptional brake on mitochondrial biogenesis (mitobiogenesis) by promoting the maturation of miR-181c, a key suppressor of mitobiogenesis that has been shown to target mitochondrial complex IV subunit I (Mtco1) and sirtuin 1 (Sirt1). Consistently, we found that a partial reduction in PACT expression is sufficient to enhance mitobiogenesis in brown adipocytes in culture as well as during BAT activation in mice. In conclusion, we demonstrate an unexpected role for PACT in the regulation of mitochondrial biogenesis and energetics in cells and BAT. © 2022 The Authors
Open Access
Small RNA-seq dataset of wild type and 16C Nicotiana benthamiana leaves sprayed with naked dsRNA using the high-pressure spraying technique
(Elsevier Inc., 2022-12) Çalışır, Kübra; Krczal, Gabi; Uslu, Veli Vural
Double-stranded RNA (dsRNA) applications have emerged as promising alternatives to chemical plant pesticides. It has been proposed that the protective effect of dsRNA is mediated by the RNA interference (RNAi) mechanism. Small RNAs (sRNAs) are one of the landmarks of RNAi mechanisms. Two classes of sRNAs appear upon RNAi, triggered by dsRNA: The cleavage products of the dsRNA mapping directly to the dsRNA sequence and the transitive sRNAs mapping to the target transcript outside of the dsRNA sequence. Therefore, the sRNA-seq data obtained from dsRNA-treated plants have been exclusively analysed in the context of the target genes and the outcome has been considered essential to evaluate the underlying mechanism of dsRNA mediated plant protection. Using high-pressure spraying technology (HPST), we have applied a GFP targeting 139bp-long dsRNA on wild type (WT) and GFP expressing (16C) Nicotiana benthamiana plants in biological triplicates. As a control, we applied water with HPST on 16C N. benthamiana. We have acquired sRNA-seq data on the treated and control leaves 5 days post spraying. In this dataset, we have expanded our sRNA-seq analysis from the target GFP transgene sequence to the whole transcriptome of N. benthamiana to provide the community with a resource for the small RNA landscape after high-pressure spraying in 16C and WT samples. Furthermore, we have provided a comparison of sRNA landscape between WT and 16C lines. © 2022 The Author(s)