Identification of an octamer-binding site controlling the activity of the small breast epithelial mucin gene promoter.
e human small breast epithelial mucin (SBEM) gene has been identified as being preferentially expressed in mammary epithelial cells and over-expressed in breast tumors. In this report, we have characterized the promoter of SBEM gene in order to identify sequences responsible for this strong mammary expression. A series of SBEM promoter/luciferase constructs were transiently transfected into both breast (MCF-7, BT-20) and non-breast (HeLa and HepG2) cell lines. In addition to the minimal promoter and to a repressor region, we have identified an 87-bp sequence (-357/-270) driving a strong breast-specific expression. Site-directed mutagenesis of a putative octamer-binding transcription factor binding site located within this latter region led to a strong decrease of the transcriptional activity of the SBEM promoter. Furthermore, transient over-expression of Oct1 and Oct2 not only increased SBEM promoter reporter activity, but also enhanced endogenous SBEM mRNA level. Overall, the data suggest that octamer-binding transcription factors participate in the strong expression of SBEM gene in breast tissues. Clarifying the SBEM gene regulation will help to dissect mechanisms underlying transcription of normal breast and breast cancer-associated genes.
Hubé
Florent
F
Department of Pathology, University of Manitoba, Winnipeg R3E 0W3, Manitoba, Canada.
Chooniedass-Kothari
Shilpa
S
Hamedani
Mohammad K
MK
Miksicek
Richard J
RJ
Leygue
Etienne
E
Myal
Yvonne
Y
D001665:Binding Sites; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D009077:Mucins / Q000096:biosynthesis* / Q000235:genetics*; D016297:Mutagenesis, Site-Directed; D050810:Octamer Transcription Factors / Q000378:metabolism*; D027701:Organic Cation Transport Proteins / Q000502:physiology; D027702:Organic Cation Transporter 1 / Q000502:physiology; D000075102:Organic Cation Transporter 2; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors; D014158:Transcription, Genetic
C511061:MUCL1 protein, human; D009077:Mucins; D050810:Octamer Transcription Factors; D027701:Organic Cation Transport Proteins; D027702:Organic Cation Transporter 1; D000075102:Organic Cation Transporter 2; C491013:SLC22A2 protein, human; D014157:Transcription Factors