SPI1 and acute promyelocytic leukemia: Stemming from our previous data demonstrating that, in APL‐derived cells treated with ATRA, some PU.1 activities are correlated with the nuclear amount of Vav1, a multidomain protein variously involved in gene expression and mRNA processing,24, 33 we explored the PU.1/Vav1 relationship during expression of miR‐29b.