ESTROGEN-RECEPTOR MESSENGER-RNA SPLICE VARIANTS PRODUCED FROM THE DISTAL AND PROXIMAL PROMOTER TRANSCRIPTS

Relative proportions of the estrogen receptor (ER) alternatively splic ed mRNA variants from the proximal (A) and distal (B) promoter pre-mRN A transcripts were measured in normal human uterus, an endometrial tum or, and in T47D, MCF-7, and BT-20 breast tumor cell lines. A single tu be RNA-PCR method was developed to determine the proportions of the in dividual transcripts and a nested, competitive RNA-PCR method to deter mine the proportions of the alternatively spliced variants. Except for the BT-20 cells, the patterns of splice variants produced from each t ranscript were very similar. In BT-20 cells no splice variants were de tected for the minor (less than or equal to 1%) A promoter transcript, although the B promoter transcript was alternatively spliced similarl y to the other samples, with the exon 7 variant as the major mRNA form . These results indicate that the mRNA spliced variant patterns in mos t tissues and tumors will be essentially unaffected by any changes in the A and B promoter ER mRNA transcript ratios that may occur. At leas t one exception does exist, however, and only more comprehensive studi es can determine whether the BT-20 cells are unique or part of a large r subgroup. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved .