Identification of two novel elements involved in human MUCI gene expression in vivo.
BACKGROUND
MUC1, a membrane-tethered glycoprotein that is expressed on a number of epithelial cell types in vivo, is over-expressed in adenocarcinomas and thought to play a significant role in tumour progression and metastasis. Hence, elucidation of the mechanisms of regulation of MUC1 gene expression is of considerable biological importance. Our aim was to evaluate regulation of MUC1 expression in vivo.


METHODS
DNase I hypersensitive sites (DHS) were mapped in chromatin from human cell lines and human MUC1 transgenic mice. MUC1 expression was evaluated by RT-PCR and Northern blots.


RESULTS
We identified two novel DHS in the MUC1 promoter at -750 bp and -250 bp from the transcriptional start site. These DHS were detected in human cell lines and in a human MUC1 transgene in mice. The -750 DHS was apparent in many cell types irrespective of the level of MUC1 expression but the -250 DHS was only evident in cells that express MUC1 and its intensity correlated with the abundance of MUC1 transcripts. The -250 DHS became undetectable in cell lines representing a transition from colon adenoma to carcinoma, commensurate with a significant reduction in MUC1 expression.


CONCLUSIONS
The -750 and -250 regions are conserved between the human MUC1 and mouse Muc1 genes and may be associated with functionally important genetic elements. The DHS at -250 is in the vicinity of previously defined purine/pyrimidine mirror repeat elements that may form intramolecular H-DNA structures, which can alter the accessibility of chromatin to regulatory proteins.
Shiraga
Toshiyuki
T
Paediatric Molecular Genetics, Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, UK.
Smith
David
D
Nuthall
Hugh N
HN
Hollingsworth
Michael A
MA
Harris
Ann
A
D000230:Adenocarcinoma / Q000235:genetics / Q000473:pathology; D000236:Adenoma / Q000235:genetics / Q000473:pathology; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D003110:Colonic Neoplasms / Q000235:genetics / Q000473:pathology; D004247:DNA / Q000235:genetics / Q000378:metabolism; D018983:DNA Footprinting; D003850:Deoxyribonuclease I / Q000378:metabolism; D018450:Disease Progression; D005786:Gene Expression Regulation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D018396:Mucin-1 / Q000096:biosynthesis / Q000235:genetics*; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D014407:Tumor Cells, Cultured
D018396:Mucin-1; D009363:Neoplasm Proteins; D004247:DNA; D003850:Deoxyribonuclease I