Project description:MIR15A and MIR16-1, located in chromosomal band 13q14, are tumor suppressor miRNAs often deleted and downregulated in chronic lymphocytic leukemia (CLL). This downregulation is not only due to loss of 13q, as it occurs also in 13q+/+ CLL patients. We found that a subgroup of CLL patients has a dysregulation of miR-15 /-16 processing intermediates due to defective processing by Drosha. These patients have reduced levels of miR-15a, miR-16 and miR-15b (another member of the miR-15 family), but not of most other miRNAs. Thus, we show that modulation of miRNA maturation leads to specific downregulation of a family of tumor suppressor miRNAs in leukemic cells. 11 normal processing CLL sample; 12 processing defective CLL patients
Project description:MIR15A and MIR16-1, located in chromosomal band 13q14, are tumor suppressor miRNAs often deleted and downregulated in chronic lymphocytic leukemia (CLL). This downregulation is not only due to loss of 13q, as it occurs also in 13q+/+ CLL patients. We found that a subgroup of CLL patients has a dysregulation of miR-15 /-16 processing intermediates due to defective processing by Drosha. These patients have reduced levels of miR-15a, miR-16 and miR-15b (another member of the miR-15 family), but not of most other miRNAs. Thus, we show that modulation of miRNA maturation leads to specific downregulation of a family of tumor suppressor miRNAs in leukemic cells.
Project description:Pleiotropic functions of miRNAs as transcriptional repressors have been reported for multiple biological processes. One prominent miRNA family is the miR-15 family, which is a well-established tumor-suppressor in B-cell chronic lymphocytic leukemia (CLL). The miR-15 family consists of three bicistronic clusters, miR-15a/16-1, miR-15b/16-2 and miR-497/195, all sharing the same seed sequence suggesting that loss one cluster can be functionally compensated by the remaining miR-15 family members. Thus, a combined deletion may be necessary to reveal its physiological function in vivo. A combined knockout of the most prominent miR-15 clusters, miR-15a/16-1 and miR-15b/16-2 in the hematopoietic system reveals a novel role of the miR-15 family in early B cell development highlighted by an increase of the pro-B cell compartment. Mechanistically, this effect is mediated by enhanced IL-7 receptor expression, which we identified as direct miR-15 target gene. Notably, elevated IL-7 receptor levels were sufficient to trigger increased activation of the STAT5 and PI3K/AKT pathways. Moreover, derepression of directly targeted cell cycle regulators such as Ccne1, Chek1 and Wee1 further facilitates G-to-S transition. Thus, by deregulating a target gene network of cell cycle and signaling mediators, loss of the miR-15 family establishes a pro-proliferative milieu manifesting in an enlarged pro-B cell pool.
Project description:NK cells develop in the bone marrow and complete their maturation in peripheral organs, but the molecular events controlling maturation are incompletely understood. Utilizing an NK cell-specific miR-15/16 deficient genetic model (15aKO), we identified a critical role for miR-15/16 family microRNAs in the normal maturation of NK cells in vivo, with a specific reduction in mature CD11b+CD27- NK cells in multiple tissues. The mechanism responsible was a block in differentiation, since accelerated NK cell death was not evident, and earlier intermediates of NK cell maturation were expanded. Further, we identified Myb as a direct target of miR-15/16 in NK cells, with Myb expression increased in immature 15aKO NK cells. Following adoptive transfer, immature 15aKO NK cells exhibited defective maturation, which was rescued by ectopic miR-15/16 expression or Myb knockdown. Moreover, Myb overexpression resulted in defective NK cell maturation. Thus, miR-15/16 regulation of Myb controls the normal NK cell maturation program.
Project description:NK cells develop in the bone marrow and complete their maturation in peripheral organs, but the molecular events controlling maturation are incompletely understood. Utilizing an NK cell-specific miR-15/16 deficient genetic model (15aKO), we identified a critical role for miR-15/16 family microRNAs in the normal maturation of NK cells in vivo, with a specific reduction in mature CD11b+CD27- NK cells in multiple tissues. The mechanism responsible was a block in differentiation, since accelerated NK cell death was not evident, and earlier intermediates of NK cell maturation were expanded. Further, we identified Myb as a direct target of miR-15/16 in NK cells, with Myb expression increased in immature 15aKO NK cells. Following adoptive transfer, immature 15aKO NK cells exhibited defective maturation, which was rescued by ectopic miR-15/16 expression or Myb knockdown. Moreover, Myb overexpression resulted in defective NK cell maturation. Thus, miR-15/16 regulation of Myb controls the normal NK cell maturation program.
Project description:MicroRNAs (miRNAs) are 20-25 nucleotides (nt) RNAs that are predicted to post-transcriptionally silence expression of >60% of all protein coding genes in mammals. As such, they form an additional layer of gene regulation that controls most if not all biological processes. MiRNAs are generated from primary transcripts containing single or multiple clustered stem-loop structures that are thought to be recognized and cleaved by the DGCR8/DROSHA Microprocessor complex as independent entities. Contrasting this view, we find that the primary miR-15a stem-loop within the bicistronic miR-15a-16-1 cluster is a poor Microprocessor substrate and is consequently not processed on its own, but that the presence of the neighboring primary miR-16-1 stem-loop on the same transcript can compensate for this deficiency in cis. Using a CRISPR/Cas9 screen, we identify SAFB2 (scaffold attachment factor B2) as an essential co-factor in this miR-16-1-assisted primary miR-15 cleavage. Small RNA sequencing further revealed that deletion of Safb1 and 2 genes reduces not only miR-15a levels, but also affects other clustered miRNAs, among them miR-15b, miR-181b and miR-92a. We therefore postulate a model in which SAFB2 enables processing of suboptimal substrates in a subset of clustered pri-miRNA transcripts.
Project description:NK cells develop in the bone marrow and complete their maturation in peripheral organs, but the molecular events controlling maturation are incompletely understood. Utilizing an NK cell-specific miR-15/16 deficient genetic model (15aKO), we identified a critical role for miR-15/16 family microRNAs in the normal maturation of NK cells in vivo, with a specific reduction in mature CD11b+CD27- NK cells in multiple tissues. The mechanism responsible was a block in differentiation, since accelerated NK cell death was not evident, and earlier intermediates of NK cell maturation were expanded. Further, we identified Myb as a direct target of miR-15/16 in NK cells, with Myb expression increased in immature 15aKO NK cells. Following adoptive transfer, immature 15aKO NK cells exhibited defective maturation, which was rescued by ectopic miR-15/16 expression or Myb knockdown. Moreover, Myb overexpression resulted in defective NK cell maturation. Thus, miR-15/16 regulation of Myb controls the normal NK cell maturation program. 3 technical replicates each of CD27+ 15a/16-1FKO NK cells, and CD27+ Ctrl NK cells
Project description:NK cells develop in the bone marrow and complete their maturation in peripheral organs, but the molecular events controlling maturation are incompletely understood. Utilizing an NK cell-specific miR-15/16 deficient genetic model (15aKO), we identified a critical role for miR-15/16 family microRNAs in the normal maturation of NK cells in vivo, with a specific reduction in mature CD11b+CD27- NK cells in multiple tissues. The mechanism responsible was a block in differentiation, since accelerated NK cell death was not evident, and earlier intermediates of NK cell maturation were expanded. Further, we identified Myb as a direct target of miR-15/16 in NK cells, with Myb expression increased in immature 15aKO NK cells. Following adoptive transfer, immature 15aKO NK cells exhibited defective maturation, which was rescued by ectopic miR-15/16 expression or Myb knockdown. Moreover, Myb overexpression resulted in defective NK cell maturation. Thus, miR-15/16 regulation of Myb controls the normal NK cell maturation program. KY-1 and KY-2 cell lines overexpressing c-Myb
Project description:MicroRNA (miRNA) biogenesis begins with Drosha cleavage, the fidelity of which is critical for downstream processing and mature miRNA target specificity. To understand how pri-miRNA sequence and structure influence Drosha cleavage, we studied the processing of three pri-miR-9 paralogs (pri-miR-9-1, pri-miR-9-2 and pri-miR-9-3), which encode the same miRNA but differ in the surrounding scaffold. We show that pri-miR-9-1 has a unique Drosha cleavage profile due to its kinked tertiary structure. Cleavage of pri-miR-9-1, but not pri-miR-9-2 or pri-miR-9-3, generates an alternative-miR-9 with a shifted seed sequence that expands the scope of its target RNAs. Here, we report the the miRNA-seq data of HEK293T and HeLa cell lines transfected with different pri-miR-9 constructs.
Project description:MicroRNA (miRNA) biogenesis begins with Drosha cleavage, the fidelity of which is critical for downstream processing and mature miRNA target specificity. To understand how pri-miRNA sequence and structure influence Drosha cleavage, we studied the processing of pri-miR-9-1 sequence variants, which encode the same mature miRNA but differ in the surrounding scaffold. We show that, in addition to previously known features, the overall structural flexibility of pri-miRNA impacts Drosha cleavage fidelity. Internal loops and nearby G·U wobble pairs on the pri-miRNA stem induce the use of non-canonical cleavage sites by Drosha, resulting in 5’ isomiR production. Here, we report the the miRNA-seq data of HEK293T cell lines transfected with different pri-miR-9 constructs.