A major focus of our pediatric
cancer research is the discovery of chemical probes to further our understanding of the biology of
leukemia harboring fusion
proteins arising from chromosomal rearrangements, and to develop novel specifically targeted
therapies. The NUP98-NSD1 fusion
protein occurs in a highly aggressive subtype of
acute myeloid leukemia after rearrangement of the genes
NUP98 and NSD1. The
methyltransferase activity of NSD1 is retained in the fusion, and it gives rise to abnormally high levels of methylation at
lysine 36 on
histone 3, enforcing oncogene activation. Therefore, inhibition of the
methyltransferase activity of NUP98-NSD1 may be considered a viable therapeutic strategy. Here, we report the development and validation of a highly sensitive and robust luminescence-based assay for NSD1 and other
methyltransferases that use
S-adenosylmethionine (SAM) as a methyl donor. The assay quantifies
S-adenosylhomocysteine (SAH), which is produced during methyl transfer from SAM. SAH is converted enzymatically to
adenosine monophosphate (
AMP); in the process,
adenosine triphosphate (
ATP) is consumed and the amount of
ATP remaining is measured using a luminescent assay kit. The assay was validated by pilot high-throughput screening (HTS), dose-response confirmation of hits, and elimination of artifacts through counterscreening against SAH detection in the absence of NSD1. The known
methyltransferase inhibitor
suramin was identified, and profiled for selectivity against the
histone methyltransferases EZH2, SETD7, and PRMT1. HTS using the luminescent NSD1 assay described here has the potential to deliver selective NSD1 inhibitors that may serve as leads in the development of targeted
therapies for NUP98-NSD1-driven
leukemias.