ABSTRACT
RNA activation (RNAa) is an uncharacterized mechanism of transcriptional activation mediated by small RNAs, such as microRNAs (miRNAs). A critical issue in RNAa research is that it is difficult to distinguish between changes in gene expression caused indirectly by post-transcriptional regulation and direct induction of gene expression by RNAa. Therefore, in this study, we seek to identify a key factor involved in RNAa, using the induction of ZMYND10 by miR-34a as a system to evaluate RNAa. We identify the positive transcription elongation factors CDK9 and DDX21, which form a complex with nuclear AGO and TNRC6A, as important transcriptional activators of RNAa. In addition, we find that inhibition of DDX21 suppresses RNAa by miR-34a and other miRNAs without inhibiting post-transcriptional regulation. Our findings reveal a strong connection between RNAa and release of paused Pol II, facilitating RNAa research by making it possible to separately analyze post-transcriptional regulation and RNAa.
Subject(s)
Cyclin-Dependent Kinase 9 , DEAD-box RNA Helicases , MicroRNAs , RNA Polymerase II , Cell Nucleus/metabolism , Cyclin-Dependent Kinase 9/metabolism , DEAD-box RNA Helicases/metabolism , Gene Expression Regulation , MicroRNAs/genetics , RNA Polymerase II/metabolism , Transcriptional ActivationABSTRACT
Bortezomib blocks the activation of nuclear factor-kappaB-mediated pro-inflammatory cytokines, however, systemic inflammatory symptoms following bortezomib administration have been reported, although their mechanisms remain elusive. Serum samples were obtained from five patients, who participated in a phase I/II study of Japanese patients with relapsed or refractory multiple myeloma (MM), and developed cyclic fever following bortezomib administration, to measure cytokine levels. Significant correlations between interleukin (IL)-6 or interferon (IFN)-gamma and the body temperature were observed in two patients each. Furthermore, we found that IL-6 elevation was not observed after the addition of bortezomib to any examined MM cells alone, but was noted in a case of bone marrow stromal cells (BMSCs) of macrophage origin alone or co-cultured with MM cells. Similarly, a marked increase in IFN-gamma levels was induced by adding bortezomib to BMSCs of fibroblast origin. Although this investigation was a preliminary study with a small number of patients, our results suggested that pro-inflammatory cytokines causing bortezomib-associated fever were secreted from BMSCs rather than MM cells.