title: Glucocorticoids modulate microRNA expression and processing during lymphocyte apoptosis.
abstract: Glucocorticoids modulate immune development and function through the induction of lymphocyte apoptosis via mechanisms requiring alterations in gene expression. Recently, short, noncoding, microRNAs have been identified as key regulators of lymphocyte function; however, it is unknown whether glucocorticoids regulate noncoding microRNAs and whether this regulation contributes to lymphocyte apoptosis. We now show by both microarray and deep sequencing analysis that microRNAs are substantially repressed during glucocorticoid-induced apoptosis of primary rat thymocytes. Mechanistic studies revealed that primary microRNA transcripts were not repressed, whereas the expression of the key microRNA processing enzymes: Dicer, Drosha, and DGCR8/Pasha, were significantly reduced at both the mRNA and protein levels during glucocorticoid-induced apoptosis. To delineate the role of Dicer depletion and microRNA repression in apoptosis, we silenced Dicer expression in two human leukemic cell lines and demonstrated that Dicer depletion significantly enhanced glucocorticoid-induced apoptosis in both model systems. Finally, in vitro and in vivo overexpression of the conserved miR-17-92 polycistron, which was repressed significantly by dexamethasone treatment in both our microarray and deep sequencing studies, blunted glucocorticoid-induced apoptosis. These studies provide evidence of altered post-transcriptional microRNA expression and the repression of the microRNA bioprocessing pathway during glucocorticoid-induced apoptosis of lymphocytes, suggesting a role for microRNA processors and specific microRNAs in cell life/death decisions.
authors.affiliation: Molecular Endocrinology Group, Laboratory of Signal Transduction, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709, USA.
authors.forename: Lindsay K
authors.initials: LK
authors.lastname: Smith
authors.forename: Ruchir R
authors.initials: RR
authors.lastname: Shah
authors.forename: John A
authors.initials: JA
authors.lastname: Cidlowski
mesh_terms: D000315:Adrenalectomy; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D017209:Apoptosis; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D016601:RNA-Binding Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D000893:Anti-Inflammatory Agents; D015415:Biomarkers; C474043:DGCR8 protein, human; D035683:MicroRNAs; D011506:Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D003907:Dexamethasone; C517918:DROSHA protein, human; D043244:Ribonuclease III