title: The miR-17-5p microRNA is a key regulator of the G1/S phase cell cycle transition.
abstract: BACKGROUND
  MicroRNAs are modifiers of gene expression, acting to reduce translation through either translational repression or mRNA cleavage. Recently, it has been shown that some microRNAs can act to promote or suppress cell transformation, with miR-17-92 described as the first oncogenic microRNA. The association of miR-17-92 encoded microRNAs with a surprisingly broad range of cancers not only underlines the clinical significance of this locus, but also suggests that miR-17-92 may regulate fundamental biological processes, and for these reasons miR-17-92 has been considered as a therapeutic target.
  
  
  RESULTS
  In this study, we show that miR-17-92 is a cell cycle regulated locus, and ectopic expression of a single microRNA (miR-17-5p) is sufficient to drive a proliferative signal in HEK293T cells. For the first time, we reveal the mechanism behind this response - miR-17-5p acts specifically at the G1/S-phase cell cycle boundary, by targeting more than 20 genes involved in the transition between these phases. While both pro- and anti-proliferative genes are targeted by miR-17-5p, pro-proliferative mRNAs are specifically up-regulated by secondary and/or tertiary effects in HEK293T cells.
  
  
  CONCLUSIONS
  The miR-17-5p microRNA is able to act as both an oncogene and a tumor suppressor in different cellular contexts; our model of competing positive and negative signals can explain both of these activities. The coordinated suppression of proliferation-inhibitors allows miR-17-5p to efficiently de-couple negative regulators of the MAPK (mitogen activated protein kinase) signaling cascade, promoting growth in HEK293T cells. Additionally, we have demonstrated the utility of a systems biology approach as a unique and rapid approach to uncover microRNA function.
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Carmody Road, St Lucia, 4072, Australia.
authors.forename: Nicole
authors.initials: N
authors.lastname: Cloonan
authors.forename: Mellissa K
authors.initials: MK
authors.lastname: Brown
authors.forename: Anita L
authors.initials: AL
authors.lastname: Steptoe
authors.forename: Shivangi
authors.initials: S
authors.lastname: Wani
authors.forename: Wei Ling
authors.initials: WL
authors.lastname: Chan
authors.forename: Alistair R R
authors.initials: AR
authors.lastname: Forrest
authors.forename: Gabriel
authors.initials: G
authors.lastname: Kolle
authors.forename: Brian
authors.initials: B
authors.lastname: Gabrielli
authors.forename: Sean M
authors.initials: SM
authors.lastname: Grimmond
mesh_terms: D002460:Cell Line; D049109:Cell Proliferation; D016193:G1 Phase / Q000502:physiology*; D006801:Humans; D035683:MicroRNAs / Q000502:physiology*; D048056:Mitogen-Activated Protein Kinase 9 / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D016196:S Phase / Q000502:physiology*; D015398:Signal Transduction
chemical_list: C524941:MIRN17 microRNA, human; D035683:MicroRNAs; D012333:RNA, Messenger; D048056:Mitogen-Activated Protein Kinase 9