I have a clone in pSecTag2Hygro B vector and I got the expression also. But I have to do transfection every time. Is there any protocol for stable transfection?
Since it is pSecTag2Hygro B vector, you should be able to select the transfected cells with hygromycin B. You need to optimize the concentration of hygromycin on the transfected cells. I am attaching a file. Hope it will help.
As you have Hygro vector. You can linearize your vector first, make sure not cut the expression elements for you target protein. Then transfect as much as you can. About one week later, you can treat with hygromycin. I you have time, you can also pick up single clone. If you don't want to linearize your vector, you can just transfect and treat hygromycin. But this efficiency is very low, and you should keep hygromycin concentration later.