The androgen receptor (AR) is a DNA-binding transcription factor that regulates genes critical for the development and maintenance of the male sexual phenotype. Defects in androgen receptor have been shown to play a role in prostate cancer, and inhibition of AR activity through modulation of signal transduction pathways may delay prostate cancer progression (Heinlein and Chang 2004). Multiple phosphorylation sites have been identified on the androgen receptor that affect cross-talk between growth factor signaling and androgen in prostate development and cancer (Gioeli et al., 2002). One of these sites, at Ser94, appears constitutively phosphorylated and exhibits no response to treatments with stimulating hormone (Gioeli et al., 2002). The site at Ser94 is unique among the AR phosphorylation sites in that it does not achieve a maximal level of phosphorylation between translation and the initial round of nuclear import, having a strong bias for androgen-independent phosphorylation in the cytoplasm (Kesler et al., 2007).
