Project description:Background & aims: MicroRNAs (miRNAs) encapsulated in EVs are potential diagnostic and prognostic biomarkers. However, discrepancies on miRNA patterns and their validation are still frequent due to differences in sample origin, EVs isolation, miRNA extraction and sequencing methods. Selecting appropriate EVs isolation methods is therefore a critical step for miRNA-based biomarker discovery. The aim of the present study is to find the most suitable EVs isolation method for miRNAs sequencing adequate for clinical application. Material & Methods EVs were isolated by Size Exclusion Chromatography (SEC), iodixanol gradients (GRAD) and the combination of both (SEC+GRAD), using the same plasma sample, in triplicate isolation assays. Isolated EVs were characterized and RNA was extracted. Three different protocols for miRNA library preparation were compared (NEBNext, NEXTFlex and SMARTer smRNA-seq) and miRNAs encapsulated on EVs were sequenced using NextSeq 500 system (Illumina). Finally, the yield, abundance and diversity of miRNAs using the three different EVs isolation protocols were analyzed and compared between them. Results The majority of lipoproteins, total cholesterol and plasma proteins were removed from the EVs-containing fractions by using SEC, GRAD, and SEC+GRAD. SEC method recovered a larger amount of EVs followed by GRAD and SEC+GRAD, while GRAD and SEC+GRAD yielded the purest vesicles. NEBNext was the library preparation kit that showed the highest reproducibility among replicas, higher number of reads corresponding to miRNAs and more different miRNAs, followed by NEXTFlex and SMARTer smRNA-seq. GRAD method showed the highest reproducibility among replicas, a higher number of reads corresponding to miRNAs and more different miRNAs, followed by SEC and SEC+GRAD methods. Conclusions These results render the GRAD method to isolate EVs as one of the most appropriate to detect miRNAs from Evs.
Project description:The elongation stage of transcription is a highly regulated in metazoan. We previously purified the AFF1/AFF4-containing Super Elongation Complex (SEC) as a major regulator of development and cancer pathogenesis. Here, we report the biochemical isolation of SEC-like 2 (SEC-L2) and SEC-like 3 (SEC-L3) containing AFF2 and AFF3 in association with P-TEFb, ENL, and AF9. The SEC family members demonstrate high levels of Pol II CTD kinase activity, however, only SEC is required for the proper induction of the HSP70 gene upon stress. Genome-wide mRNA-seq analyses demonstrate that SEC-L2-3 control the expression of different subsets of genes, while AFF4/SEC plays a more dominant role in rapid gene expression in cells. MYC is one of the direct targets of AFF4/SEC, and the SEC requirement to the MYC gene regulates its expression in different cancer cells bearing either acute myeloid or lymphoid leukemia. These findings suggest that AFF4/SEC could be a potential therapeutic target for the treatment of leukemia or other cancers associated with MYC overexpression.
Project description:To test whether Brd4 and SEC co-regulate the release of promoter-proximally paused Pol II, we performed Pol II ChIP-Seq to analyze the effect of depletion of Brd4 or SEC on HMBA-induced pause release in HCT116 cells.
Project description:uSTAT transcriptional program HPC7 cells were fixed with either 1% formaldehyde for 10 mins. Chromatin was isolated, sonicated for 7 mins (30 sec on, 30 sec off), and specific antibodies were used to pull down the transcription factors of insterest after a pre-clearing step. Chromatin was washed, de-crosslinked, amplified, size selected by gel purification and sequenced.
Project description:The regulation of gene expression catalyzed by RNA Polymerase II (Pol II) requires a host of accessory factors to ensure cell growth, differentiation, and survival under environmental stress. Here, using the auxin-inducible degradation (AID) system to study transcriptional activities of the bromodomain and extra terminal domain (BET) and Super Elongation Complex (SEC) families, we found that the CDK9-containing BRD4 complex is required for the release of Pol II from promoter-proximal pausing for most genes, while the CDK9-containing SEC is required for activated transcription in the heat shock response. By using both the Proteolysis-targeting chimera (PROTAC) dBET6 and the AID system, we found that dBET6 treatment results in two major effects: the increased pausing due to BRD4 loss, and reduced enhancer activity attributable to BRD2 loss. In the heat shock response, while auxin-mediated depletion of the AFF4 subunit of SEC has a more severe defect than AFF1 depletion, simultaneous depletion of AFF1 and AFF4 leads to a stronger attenuation of the heat shock response, similar to treatment with the SEC inhibitor KL-1, suggesting a possible redundancy among SEC family members. This study highlights the usefulness of orthogonal acute depletion/inhibition strategies to identify distinct and redundant biological functions among Pol II elongation factor paralogs.
Project description:The aim of this study was to determine the genomic binding sites of important haematopoietic transcription factors in haematopoietic cell lines. 416Bs cells were fixed with either 1 or 0.4 % formaldehyde for 10 mins. Chromatin was isolated, sonicated for 7 mins (30 sec on, 30 sec off), and specific antibodies were used to pull down the transcription factors of interest after a pre-clearing step. Chromatin was washed, de-crosslinked, amplified, size selected by gel purification and sequenced.
Project description:The AF4/FMR2 proteins AFF1 and AFF4 act as a scaffold to assemble the Super Elongation Complex (SEC) that strongly activates transcriptional elongation of HIV-1 and cellular genes. Although they can dimerize, it is unclear whether the dimers exist and function within a SEC in vivo. Furthermore, it is unknown whether AFF1 and AFF4 function similarly in mediating SEC-dependent activation of diverse genes. Providing answers to these questions, our current study shows that AFF1 and AFF4 reside in separate SECs that display largely distinct gene target specificities. While the AFF1-SEC is more potent in supporting HIV-1 transactivation by the viral Tat protein, the AFF4-SEC is more important for HSP70 induction upon heat shock. The functional difference between AFF1 and AFF4 in Tat-transactivation has been traced to a single amino acid variation between the two proteins, which causes them to enhance the affinity of Tat for P-TEFb, a key SEC component, with different efficiency. Finally, genome-wide analysis confirms that the genes regulated by AFF1- and AFF4-SEC are largely non-overlapping and perform distinct functions. Thus, the SEC represents a family of related complexes that exist to increase the regulatory diversity and gene control options during transactivation of diverse cellular and viral genes.
Project description:New methods for the global identification of RNA-protein interactions have led to greater recognition of the abundance and importance of RNA-binding proteins (RBPs) in bacteria. Here, we expand this tool kit by developing SEC-seq, a method based on a similar concept as the established Grad-seq approach. In Grad-seq, cellular RNA and protein complexes of a bacterium of interest are separated in a glycerol gradient, followed by high-throughput RNA-sequencing and mass spectrometry analyses of individual gradient fractions. New RNA-protein complexes are predicted based on the similarity of their elution profiles. In SEC-seq, we have replaced the glycerol gradient with separation by size exclusion chromatography, which shortens operation times and offers greater potential for automation. Applying SEC-seq to Escherichia coli, we find that the method provides a higher resolution than Grad-seq in the lower molecular weight range up to ~500 kDa. This is illustrated by the ability of SEC-seq to resolve two distinct, but similarly sized complexes of the global translational repressor CsrA with either of its antagonistic small RNAs, CsrB and CsrC. We also characterized changes in the SEC-seq profiles of the small RNA MicA upon deletion of its RNA chaperones Hfq and ProQ and investigated the redistribution of these two proteins upon RNase treatment. Overall, we demonstrate that SEC-seq is a tractable and reproducible method for the global profiling of bacterial RNA-protein complexes that offers the potential to discover yet-unrecognized associations between bacterial RNAs and proteins.