The unusual structural properties and potential biological relevance of switchback DNA.

Synthetic DNA motifs form the basis of nucleic acid nanotechnology, and their biochemical and biophysical properties determine their applications. Here, we present a detailed characterization of switchback DNA, a globally left-handed structure composed of two parallel DNA strands. Compared to a conventional duplex, switchback DNA shows lower thermodynamic stability and requires higher magnesium concentration for assembly but exhibits enhanced biostability against some nucleases. Strand competition and strand displacement experiments show that component sequences have an absolute preference for duplex complements instead of their switchback partners. Further, we hypothesize a potential role for switchback DNA as an alternate structure in sequences containing short tandem repeats. Together with small molecule binding experiments and cell studies, our results open new avenues for switchback DNA in biology and nanotechnology.

A global analysis on the differential regulation of RNA binding proteins (RBPs) by TNF-α as potential modulators of metabolic syndromes.

Metabolic syndrome (MetS) is associated with a group of conditions, which enhances the risk of diabetes, heart diseases and stroke in the affected individuals. Earlier reports from our lab have shown that Tumor necrosis factor-α (TNF-α) significantly modulates the expression of 56 genes at the alternative splicing level which are involved in various signaling and metabolic pathways (MetS genes) connected to MetS. These MetS genes were predicted to interact with various RNA-binding proteins (RBPs) when exposed to TNF-α, resulting changes in their alternative splicing patterns. Here we are presenting data of an RNA-Seq analysis, which identified 1218 unique, and significantly regulated genes by TNF-α, 15% of which are RBPs . Among the 1218 genes, 204 genes have been identified as MetS genes by the ingenuity pathway analysis, and 10% of the MetS genes are found as RBPs. Our results also show that TNF-α changes the phosphorylation status of certain RBPs such as SR proteins, crucial players in alternative splicing, possibly via changing the activation status of certain upstream signaling molecules which also act as upstream kinases for these proteins. Taken together, these findings suggest that TNF-α influences the regulation of the RBPs at the various levels for their expression, which may lead to the alteration of the splicing pattern of the MetS genes. MetS genes acting as RBPs and are modulated by TNF-α, predict the existence of highly interconnected mechanisms which require further analysis to understand their dual roles on the onset of these diseases.

Global analysis of RNA-protein interactions in TNF-α induced alternative splicing in metabolic disorders.

In this report, using the database of RNA-binding protein specificities (RBPDB) and our previously published RNA-seq data, we analyzed the interactions between RNA and RNA-binding proteins to decipher the role of alternative splicing in metabolic disorders induced by TNF-α. We identified 13 395 unique RNA-RBP interactions, including 385 unique RNA motifs and 35 RBPs, some of which (including MBNL-1 and 3, ZFP36, ZRANB2, and SNRPA) are transcriptionally regulated by TNF-α. In addition to some previously reported RBPs, such as RBMX and HuR/ELAVL1, we found a few novel RBPs, such as ZRANB2 and SNRPA, to be involved in the regulation of metabolic syndrome-associated genes that contain an enrichment of tetrameric RNA sequences (AUUU). Taken together, this study paves the way for novel RNA-protein interaction-based therapeutics for treating metabolic syndromes.

TNF-alpha regulates alternative splicing of genes participating in pathways of crucial metabolic syndromes; a transcriptome wide study.

BACKGROUND: TNF-α, a pro-inflammatory cytokine is one of the major contributors for metabolic syndromes including insulin resistance, obesity, type II diabetes etc. The role of alternative splicing, a post-transcriptional regulation of gene expression on the onset of these syndromes is poorly understood. However, the role of alternative splicing, which more than 95% of all exons in eukaryotic cells undergo in several other diseases including cancer and muscle dystrophy, has been elucidated. In this study we aim to investigate the role of alternative splicing in pathways leading to metabolic syndromes mediated by TNF-α. METHODS: A genome wide transcriptome analysis was carried out using Illumina platform. Results were validated using RT-PCR analysis. Various bioinformatics tools and databases (for example IPA, KEGG, STRING etc) were used for the pathway and interactome analysis. CURRENT FINDINGS: Transcriptome wide analysis revealed that TNF-α treatment in vitro causes a significant change in expression of 228 genes at the level of alternative splicing. Regulation of some of these genes was validated in different cell lines. Pathway analysis showed at least 15% of the alternatively spliced genes fall under the contributory pathways leading to different metabolic syndromes, among which the maximally interconnected genes were transcription regulators. CONCLUSION: These findings suggest that TNF-α.-mediated alternative splicing plays a crucial role in regulating various genes involved in pathways connected to metabolic syndromes.

A novel reporter construct for screening small molecule inhibitors that specifically target self-renewing cancer cells.

Cancer stem cells (CSCs) are a subset of cancer cells, which possess self-renewal ability, and lead to tumor progression, metastasis, and resistance to therapy. Live detection and isolation of CSCs are important to understand the biology of CSCs as well as to screen drugs that target them. Even though CSCs are detected using surface markers, there is a lot of inconsistencies for that in a given cancer type. At the same time, self-renewal markers like ALDH1A1, OCT4A and SOX2, which are intracellular molecules, are reliable markers for CSCs in different cancers. In the present study, we generated a reporter construct for self-renewing CSCs, based on ALDH1A1 expression. Oral cancer cells harboring ALDH1A1-DsRed2 were used to screen inhibitors that target CSCs. Our results showed that Comb1, a cocktail of inhibitors for EGF and TGF-ß pathways and their intermediates, effectively reduced the DsRed2 population to 34%. Our immunohistochemical analysis on primary oral cancer corroborated the importance of EGF and TGF-ß pathways in sustaining CSCs. Since these two pathways are also critical for the self-renewal and differentiation of normal stem cells, Comb1 might abolish them as well. On analysis of the effect of Comb1 on normal murine bone marrow cells, there was no significant change in the stem cell self-renewal and differentiation potential in the treated group compared to untreated cells. To conclude, we claim that ALDH1A1-DsRed2 is a useful tool to detect CSCs, and Comb1 is effective in targeting CSCs without affecting normal stem cells.

TM1-IR680 peptide for assessment of surgical margin and lymph node metastasis in murine orthotopic model of oral cancer.

Treatment outcome after surgical removal in oral carcinoma is poor due to inadequate methodologies available for marking surgical margins. Even though some methodologies for intraoperative margin assessment are under clinical and preclinical trials for other solid tumours, a promising modality for oral cancer surgery is not developed. Fluorescent-based optical imaging using Near Infrared (NIR) dyes tagged to tumour specific target will be an optimal tool for this purpose. One such target, Gastrin Releasing Peptide Receptor (GRPR) was selected for the study, and its binding peptide, TM1-IR680, was tested for its efficacy for surgical margin prediction in murine orthotopic model of oral cancer, derived from primary samples. Here, for the first time in a preclinical analysis, we show that the size and margin of oral cancer can be predicted, as revealed by 3D-imaging. Interestingly, the peptide was sensitive enough to detect lymph nodes that harboured dispersed tumour cells before colonization, which was impossible to identify by conventional histopathology. We recommend the use of TM1-NIR dyes alone or in combination with other technologies to improve the clinical outcome of oral cancer surgery.

Live detection and purification of cells based on the expression of a histone chaperone, HIRA, using a binding peptide.

Flow cytometry is a reliable method for identification and purification of live cells from a heterogeneous population. Since permeabilized cells cannot be sorted live in a FACS sorter, its application in isolation of functional cells largely depends on antibodies for surface markers. In various fields of biology we find intracellular markers that reveal subpopulations of biological significance. Cell cycle stage specific molecules, metastatic signature molecules, stemness associated proteins etc. are examples of potential markers that could improve the research and therapy enormously. Currently their use is restricted by lack of techniques that allow live detection. Even though a few methods like aptamers, droplet-based microfluidics and smartflares are reported, their application is limited. Here, for the first time we report a simple, cost-effective and efficient method of live sorting of cells based on the expression of an intracellular marker using a fluorophore-tagged binding peptide. The target molecule selected was a histone chaperone, HIRA, the expression of which can predict the fate of differentiating myoblast. Our results confirm that the peptide shows specific interaction with its target; and it can be used to separate cells with differential expression of HIRA. Further, this method offers high purity and viability for the isolated cells.