The mixed lineage leukaemia (MLL) gene is frequently the target of chromosomal
translocation in infant leukaemia. Translocation results in an in-frame chimeric fusion
gene which is implicated in both ALL and AML, with particularly poor prognoses. It is
widely accepted that MLL has a crucial role in regulating haematopoiesis. Our lab has
previously developed a murine model for conditional expression of MLL-fusions to
establish a list of transcriptional target genes using Affymetrix GeneChip analysis. In
order to study the role of MLL-fusion target genes in human leukaemia cells, we
generated four independent immortalised myeloid cell lines from human cord blood,
using the MLL-AF9 fusion, by means of lentiviral transduction. The transduced cells
proliferated exponentially in liquid culture and were found to cause leukaemia upon
xenotransplantation into immunodeficient mice. One of the target genes up-regulated
by the MLL-fusions, RUVBL2, encodes an ATPase belonging to AAA+ family that has
multiple roles in telomerase and chromatin-remodelling complexes. In this study, we
demonstrate that RUVBL2 is also up-regulated by MLL-AF9 in human immortalised
myeloid cells. shRNA knock down of RUVBL2 expression in these cells, and in the
human leukaemia cell line THP-1, results in decreased cell proliferation and clonogenic
potential, accompanied by an increase in apoptosis and differentiation, as judged by
CD15 expression. Furthermore, inhibition of RUVBL2 expression in THP-1 cells leads
to a reduction in hTERT mRNA expression and telomerase activity. Together, these
data demonstrate the requirement of RUVBL2 to mediate MLL-fusion induced
telomerase activity in human cells, and suggest the possibility of targeting RUVBL2 as
a potential therapeutic strategy for MLL-fusion associated leukaemia
