Project description:BACKGROUND: Transcription of large numbers of non-coding RNAs originating from intronic regions of human genes has been recently reported, but mechanisms governing their biosynthesis and biological functions are largely unknown. In this work, we evaluated the existence of a common mechanism of transcription regulation shared by protein-coding mRNAs and intronic RNAs by measuring the effect of androgen on the transcriptional profile of a prostate cancer cell line. RESULTS: Using a custom-built cDNA microarray enriched in intronic transcribed sequences, we found 39 intronic non-coding RNAs for which levels were significantly regulated by androgen exposure. Orientation-specific reverse transcription-PCR indicated that 10 of the 13 were transcribed in the antisense direction. These transcripts are long (0.5-5 kb), unspliced and apparently do not code for proteins. Interestingly, we found that the relative levels of androgen-regulated intronic transcripts could be correlated with the levels of the corresponding protein-coding gene (asGAS6 and asDNAJC3) or with the alternative usage of exons (asKDELR2 and asITGA6) in the corresponding protein-coding transcripts. Binding of the androgen receptor to a putative regulatory region upstream from asMYO5A, an androgen-regulated antisense intronic transcript, was confirmed by chromatin immunoprecipitation. CONCLUSIONS: Altogether, these results indicate that at least a fraction of naturally transcribed intronic non-coding RNAs may be regulated by common physiological signals such as hormones, and further corroborate the notion that the intronic complement of the transcriptome play functional roles in the human gene-expression program. Keywords: Time course study – effect of androgen on gene expression
Project description:Approximately half of all microRNAs reside within intronic regions and are often co-transcribed with their host genes. However, most studies on intronic microRNAs focus on individual microRNAs, and conversely most studies on protein-coding and non-coding genes frequently ignore any intron-derived microRNAs. We hypothesize that the individual components of such multi-genic loci may play cooperative or competing roles in driving disease progression, and that examining the combinatorial effect of these components would uncover deeper insights into their functional importance. To address this, we perform systematic analyses of intronic microRNA:host loci in colon cancer. We observe that the FTX locus, comprising of a long non-coding RNA FTX and multiple intronic microRNAs, is highly upregulated in cancer and demonstrate that cooperativity within this multi-component locus promotes cancer growth. In addition, we show that FTX interacts with DHX9 and DICER and delineate its novel roles in regulating A-to-I RNA editing and microRNA expression. These results show for the first time that a long non-coding RNA can regulate A-to-I RNA editing, further expanding the functional repertoire of long non-coding RNAs. We further demonstrate the inhibitory effects of intronic miR-374b and -545 on the tumor suppressors PTEN and RIG-I to enhance the proto-oncogenic PI3K-AKT signaling. Finally, we show that intronic miR-421 may exert an autoregulatory effect on miR-374b and -545. Taken together, our data unveil the intricate interplay between intronic microRNAs and their host transcripts in the modulation of key signaling pathways and disease progression, adding new perspectives to the functional landscape of multi-genic loci.
Project description:Interventions: Case series:Nil
Primary outcome(s): intestinal microecological disorders;blood non-coding RNAs and immune status
Study Design: Randomized parallel controlled trial
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.