Analysis of Transcriptional Regulation of the Human miR-17-92 Cluster; Evidence for Involvement of Pim-1

• Main Authors: Roland K. Hartmann, Achim Aigner, Arnold Grünweller, Dennis Streng, Julia Schlereth, Lara Golde, Kerstin Lange-Grünweller, Dorothee Hartmann, Maren Thomas
• Format: Article
• Language: English
• Published: MDPI AG 2013-06-01
• Series: International Journal of Molecular Sciences
• Subjects: miRNA; miR-17-92 cluster; Pim-1; miRNA promoter; c-Myc; HP1γ; RNAi
• Online Access: http://www.mdpi.com/1422-0067/14/6/12273

The human polycistronic miRNA cluster miR-17-92 is frequently overexpressed in hematopoietic malignancies and cancers. Its transcription is in part controlled by an E2F-regulated host gene promoter. An intronic A/T-rich region directly upstream of the miRNA coding region also contributes to cluster expression. Our deletion analysis of the A/T-rich region revealed a strong dependence on c-Myc binding to the functional E3 site. Yet, constructs lacking the 5'-proximal ~1.3 kb or 3'-distal ~0.1 kb of the 1.5 kb A/T-rich region still retained residual specific promoter activity, suggesting multiple transcription start sites (TSS) in this region. Furthermore, the protooncogenic kinase, Pim-1, its phosphorylation target HP1γ and c-Myc colocalize to the E3 region, as inferred from chromatin immunoprecipitation. Analysis of pri-miR-17-92 expression levels in K562 and HeLa cells revealed that silencing of E2F3, c-Myc or Pim-1 negatively affects cluster expression, with a synergistic effect caused by c-Myc/Pim-1 double knockdown in HeLa cells. Thus, we show, for the first time, that the protooncogene Pim-1 is part of the network that regulates transcription of the human miR-17-92 cluster.