Abstract

The human mucin 4 (MUC4) is aberrantlyexpressed in pancreatic adenocarcinoma and tumor cell lines, while remainingundetectable in normal pancreas, indicating its important role in pancreaticcancer development. Although its transcriptional regulation has beeninvestigated in considerable detail, some important elements remain unknown.The aim of the present study was to demonstrate the existence of a novelinhibitory element in the MUC4 promoter and characterize some of its bindingproteins. By luciferase reporter assay, we located the inhibitory elementbetween nucleotides -2530 and -2521 in the MUC4 promoter using a series of deletionand mutant reporter constructs. Electrophoretic mobility shift assay (EMSA)with Bxpc-3 cell nuclear extracts revealed that one protein or protein complexbind to this element. The proteins binding to this element were purified andidentified as Yin Yang 1 (YY1) by mass spectrometry. Supershift assay andchromatin immunoprecipitation (ChIP) assay confirmed that YY1 binds to thiselement in vitro and in vivo. Moreover, transient YY1 overexpressionsignificantly inhibited MUC4 promoter activity and endogenous MUC4 proteinexpression. In conclusion, we reported here a novel inhibitory element in thehuman MUC4 promoter. This provides additional data on MUC4 gene regulation andindicates that YY1 may be a potential target for abnormal MUC4 expression.