title: miR-125b and miR-155 contribute to BCL2 repression and proliferation in response to CD40 ligand (CD154) in human leukemic B-cells.
abstract: Developmental stage-specific regulation of BCL2 occurs during B-cell maturation and has a role in normal immunity. CD40 signaling promotes proliferation and rescues B-cells from apoptosis, partly through induction of BCL2L1 and BCL2A1 and repression of BCL2. We previously showed that a stromal cell/CD40 ligand (CD154) culture system reproduced this switch in survival protein expression in primary human leukemic B-cells and we employed this model system to investigate BCL2 repression. BCL2 was post-transcriptionally regulated and the repressed BCL2 mRNA was associated with non-polysomal, but dense fractions on sucrose density gradients. Microarrays identified a set of miRNA that were induced by culture conditions and potentially able to bind to the BCL2 3'-UTR. Luciferase reporter assays demonstrated that miR-125b and miR-155 repressed BCL2 mRNA but while stromal cell contact alone was sufficient to induce strongly miR-125b this did not cause BCL2 repression. miR-155, which is the most abundant miRNA under basal conditions, specifically required CD154 for further induction above a threshold to exert its full repressive effects. Anti-miR-125b and anti-miR-155 prevented CD154-mediated repression of BCL2 and reduced CD154-mediated proliferation in the MEC1 B-cell line. We suggest that miR-155 and miR-125b, which are induced by CD154 and stromal cell signals, contribute to regulating proliferation and that BCL2 is one of their target mRNAs.
authors.affiliation: Department of Cancer Studies and Molecular Medicine and MRC Toxicology Unit, University of Leicester, Leicester LE19HN, United Kingdom.
authors.forename: Shaun
authors.initials: S
authors.lastname: Willimott
authors.forename: Simon D
authors.initials: SD
authors.lastname: Wagner
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D023201:CD40 Ligand / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015973:Gene Expression Regulation, Leukemic; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000378:metabolism*; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; C531888:MIRN125 microRNA, human; C524942:MIRN155 microRNA, human; D035683:MicroRNAs; D019253:Proto-Oncogene Proteins c-bcl-2; D012334:RNA, Neoplasm; D023201:CD40 Ligand