The WT1 gene is a key player in acute myeloid leukaemia, in which it is frequently over-expressed. WT1 encodes a multifunctional zinc finger protein transcription factor, which also binds mRNA. Thus increasing evidence suggests that WT1 works both at the DNA and mRNA level, not only in the urogenital system but also in other contexts. Nuclear poly(A)(+) mRNP particles were isolated by oligo(dT) chromatography from the human acute myeloid leukemia cell lines HL60 and K562, and analysed by Western blotting and 2D minigels. MALDI-TOF demonstrated the presence of hnRNP proteins, splice factors, and unexpectedly vimentin in the mRNP fraction. WT1 was also shown to be present in nuclear mRNP particles suggesting that in leukaemia, and by extension in all cancers in which it is involved, WT1 works both at the DNA and mRNA target level.