Anyone has experience in using estrogen receptor (ER) fusion protein? - (May/31/2013 )

Hi, guys. These days I need to study a protein funtion in nucleus. So I constructed vector expressed estrogen receptor (ER) and estrogen receptor (ER) fusion protein. Then I transfected 293T cell with these vector to detect ER and ER fusion protein expression by western blot and immunofluorescence. The ER fusion protein expression can be detected when cell did not treat with 4-OHT and can be induced to translocate to nucleus by treating with 4-Hydroxytamoxifen (4-OHT). However, the ER (did not fuse with others protein) expression can not be detected when cell did not treat with 4-OHT. Is this normal? Please help!!!

, oh, somebody help me!!!