passages.id: split_5_test_1131_passage
passages.type: progene_text
passages.text: We demonstrate that (a) mutations within either the C / EBP or CRE site have no impact on basal or cholesterol - mediated repression of LDLR transcription , but they completely abolish OM - mediated activation of LDLR transcription ; ( b ) replacing the repeat 3 sequence that contains the Sp1 - binding site with a yeast transcription factor GAL4 - binding site in the LDLR promoter construct does not affect OM inducibility , thereby demonstrating that OM induction is mediated through the SIRE sequence in conjunction with a strong activator bound to the repeat 3 sequence ; ( c ) electrophoretic mobility shift and supershift assays confirm the specific binding of transcription factors C / EBP and cAMP - responsive element - binding protein to the SIRE ; ( d ) cotransfection of a human C / EBPbeta expression vector ( pEF-NFIL6 ) with the LDLR promoter construct pLDLR234 increases LDLR promoter activity ; and ( e ) OM and dibutyryl cAMP synergistically activate LDLR transcription through this regulatory element .