Oncogenic potential of the miR-106-363 cluster and its implication in human T-cell leukemia

We previously reported the identification of the Kis2 common retrovirus integration site, located on mouse chromosome X, in radiation leukemia virus-induced T-cell leukemias. Tumors with a provirus at the Kis2 locus overexpressed a novel noncoding RNA (ncRNA) with a complex splicing pattern and no polyA tail. Database upgrade revealed the presence of a microRNA (miRNA) cluster, miR-106-363, just downstream of the Kis2 ncRNAs. We found that Kis2 ncRNAs are the primiRNA of miR-106-363, and we present evidence that Kis2 ncRNA overexpression in mouse tumors results in miR-106a, miR-19b-2, mill-92-2, and mill-20b accumulation. We show the oncogenic potential of those miRNAs in anchorage independence assay and confirm pri-miR-106-363 overexpression in 46% of human T-cell leukemias tested. This overexpression contributes in rising mill-92 and mill-19 levels, as this is the case for miR-17-92 cluster overexpression. Furthermore, we identified myosin regulatory light chain-interacting protein, retinoblastoma-binding protein 1-like, and possibly homeodomain-interacting protein kinase 3 as target genes of this miRNA cluster, which establishes a link between these genes and T-cell leukemia for the first time.