Splice factors and intron sequences involved in alternative splicing of Scavenger Receptor Class B gene

Scavenger receptor class B type 1 (SRB1) mediates selective hepatic uptake of high density lipoprotein (HDL) lipids promoting reverse cholesterol transport. Previously we and others have demonstrated that estrogen (E) modulates SRB alternative splicing by decreasing SRB1 expression and increasing the splice variant SRB2. The ratio of SRB2 and SRB1 may be critical in E regulation of HDL levels. This study identifies cis ‐ and trans ‐regulators of SRB alternative splicing and identifies a mechanism for E regulation in this process. For these studies a SRB minigene was constructed containing minimal genomic sequence adjacent to the skipped exon region and a series of intronic deletions were analyzed for regulatory sequences that modulate exon inclusion. Two intron sequences were found to be critical for exon inclusion. In addition, over‐expression of the splice factors SF2/ASF and Tra2β were shown to change the ratio of SRB2 and SRB1 dramatically while others, hnRNP‐G, SC‐35, and SRp40, had no effect. An essential role for Tra2β in SRB2 regulation was further supported by the fact that rats treated with E had increased Tra2β protein levels further suggesting an essential role for this factor in E‐mediated SRB alternative splicing. In conclusion, this study identifies for the first time crucial intron sequences and splice factors that mediate E regulated SRB alternative splicing. Supported by NIH HL078817.