SDS-PAGE high MW protein trapped - 250 kDa protein is trapped at the interface (Nov/14/2004 )

Currently, i m prepareing a western blot for probing RNA pol II. in my western blot, i found that the protein band is trapped between the stacking and separating gel. the protein samples are boil 5 min, 95C with SDS and beta-mercap. the problem have not yet solved. Can anyone give me suggestion?

thanks Serglom,

i m using a 6% separating gel already. any other clues can result in this problem?

maybe try to denature in 8M urea...