HSP90AB1 and leukemia: Importantly, many previous studies have shown that CK II phosphorylates S231 and S226 in human Hsp90α and Hsp90β (Lees-Miller and Anderson, 1989), the equivalent residues have high homology with Drosophila Hsp83, respectively, that are essential for chemoresistance in leukemias or for the formation of the functional cytosolic aryl hydrocarbon receptor complex (Ogiso et al., 2004; Kurokawa et al., 2008).