Is cross-species horizontal gene transfer responsible for gallbladder carcinogenesis.

BACKGROUND: Cross-species horizontal gene transfer (HGT) involves the transfer of genetic material between different species of organisms. In recent years, mounting evidence has emerged that cross-species HGT does take place and may play a role in the development and progression of diseases. METHODS: Transcriptomic data obtained from patients with gallbladder cancer (GBC) was assessed for the differential expression of antisense RNAs (asRNAs). The Basic Local Alignment Search Tool (BLAST) was used for cross-species analysis with viral, bacterial, fungal, and ancient human genomes to elucidate the evolutionary cross species origins of these differential asRNAs. Functional enrichment analysis and text mining were conducted and a network of asRNAs targeting mRNAs was constructed to understand the function of differential asRNAs better. RESULTS: A total of 17 differentially expressed antisense RNAs (asRNAs) were identified in gallbladder cancer tissue compared to that of normal gallbladder. BLAST analysis of 15 of these asRNAs (AFAP1-AS1, HMGA2-AS1, MNX1-AS1, SLC2A1-AS1, BBOX1-AS1, ELFN1-AS1, TRPM2-AS, DNAH17-AS1, DCST1-AS1, VPS9D1-AS1, MIR1-1HG-AS1, HAND2-AS1, PGM5P4-AS1, PGM5P3-AS1, and MAGI2-AS) showed varying degree of similarities with bacterial and viral genomes, except for UNC5B-AS1 and SOX21-AS1, which were conserved during evolution. Two of these 15 asRNAs, (VPS9D1-AS1 and SLC2A1-AS1) exhibited a high degree of similarity with viral genomes (Chikungunya virus, Human immunodeficiency virus 1, Stealth virus 1, and Zika virus) and bacterial genomes including (Staphylococcus sp., Bradyrhizobium sp., Pasteurella multocida sp., and, Klebsiella pneumoniae sp.), indicating potential HGT during evolution. CONCLUSION: The results provide novel evidence supporting the hypothesis that differentially expressed asRNAs in GBC exhibit varying sequence similarity with bacterial, viral, and ancient human genomes, indicating a potential shared evolutionary origin. These non-coding genes are enriched with methylation and were found to be associated with cancer-related pathways, including the P53 and PI3K-AKT signaling pathways, suggesting their possible involvement in tumor development.

Revisiting the coding potential of the E. coli genome through Hfq co-immunoprecipitation.

Hfq is a global regulator of gene expression in bacteria undergoing adaptation to changing environmental conditions. Its major function is to promote RNA-RNA interactions between regulatory small RNAs (sRNAs) and their target mRNAs. Previously, we demonstrated that Hfq binds many antisense RNAs (asRNAs) in vitro and hypothesized that Hfq may play a role in regulating gene expression via asRNAs. To investigate the E. coli Hfq-binding transcriptome in more detail, we co-immunoprecipitated and deep-sequenced RNAs bound to Hfq in vivo. We detected many new Hfq-binding sRNAs and observed that almost 300 mRNAs bind to Hfq. Among these, several are known to be sRNA targets. We identified 25 novel RNAs, which are transcribed from within protein coding regions and named them intragenic RNAs (intraRNAs). Furthermore, 67 asRNAs were co-immunoprecipitated with Hfq, demonstrating that Hfq binds antisense transcripts in vivo. Northern blot analyses confirmed the deep-sequencing results and demonstrated that many of the novel Hfq-binding RNAs identified are regulated by Hfq.

Regulatory Interplay between RNase III and Antisense RNAs in E. coli: the Case of AsflhD and FlhD, Component of the Master Regulator of Motility.

In order to respond to ever-changing environmental cues, bacteria display resilient regulatory mechanisms controlling gene expression. At the post-transcriptional level, this is achieved by a combination of RNA-binding proteins, such as ribonucleases (RNases), and regulatory RNAs, including antisense RNAs (asRNAs). Bound to their complementary mRNA, asRNAs are primary targets for the double-strand-specific endoribonuclease, RNase III. Taking advantage of our own and previously published transcriptomic data sets obtained in strains inactivated for RNase III, we selected several candidate asRNAs and confirmed the existence of RNase III-sensitive asRNAs for crp, ompR, phoP, and flhD genes, all encoding global regulators of gene expression in Escherichia coli. Using FlhD, a component of the master regulator of motility (FlhD4C2), as our model, we demonstrate that the asRNA AsflhD, transcribed from the coding sequence of flhD, is involved in the fine-tuning of flhD expression and thus participates in the control of motility. IMPORTANCE The role of antisense RNAs (asRNAs) in the regulation of gene expression remains largely unexplored in bacteria. Here, we confirm that asRNAs can be part of layered regulatory networks, since some are found opposite to genes encoding global regulators. In particular, we show how an antisense RNA (AsflhD) to the flhD gene, encoding the transcription factor serving as the primary regulator of bacterial swimming motility (FlhD4C2), controls flhD expression, which in turn affects the expression of other genes of the motility cascade. The role of AsflhD highlights the importance of fine-tuning mechanisms mediated by asRNAs in the control of complex regulatory networks.

The world of asRNAs in Gram-negative and Gram-positive bacteria.

Bacteria exhibit an amazing diversity of mechanisms controlling gene expression to both maintain essential functions and modulate accessory functions in response to environmental cues. Over the years, it has become clear that bacterial regulation of gene expression is still far from fully understood. This review focuses on antisense RNAs (asRNAs), a class of RNA regulators defined by their location in cis and their perfect complementarity with their targets, as opposed to small RNAs (sRNAs) which act in trans with only short regions of complementarity. For a long time, only few functional asRNAs in bacteria were known and were almost exclusively found on mobile genetic elements (MGEs), thus, their importance among the other regulators was underestimated. However, the extensive application of transcriptomic approaches has revealed the ubiquity of asRNAs in bacteria. This review aims to present the landscape of studied asRNAs in bacteria by comparing 67 characterized asRNAs from both Gram-positive and Gram-negative bacteria. First we describe the inherent ambiguity in the existence of asRNAs in bacteria, second, we highlight their diversity and their involvement in all aspects of bacterial life. Finally we compare their location and potential mode of action toward their target between Gram-negative and Gram-positive bacteria and present tendencies and exceptions that could lead to a better understanding of asRNA functions.