Harris Laboratory
Ann Harris Group
Chromatin Structure and the Regulation of Gene Expression:
The CFTR (cystic fibrosis transmembrane conductance regulator) gene, which when mutated causes cystic fibrosis, encompasses nearly 200 kb of genomic DNA at chromosome 7q31.2. Despite its highly regulated pattern of expression, the promoter of the CFTR gene apparently lacks the necessary elements to achieve this. We previously suggested that cis-acting regulatory elements elsewhere in the locus, both flanking the gene and within introns, were required to coordinate regulated, tissue-specific expression of CFTR. A number of crucial elements were identified, including enhancer-blocking insulators flanking the locus, intronic tissue-specific enhancers and some of the interacting proteins were characterized. We recently employed a high-resolution method of mapping DHS (DNase I-hypersensitive sites) using tiled microarrays. DHS are often associated with regulatory elements and use of this technique generated cell-specific profiles of potential regulatory sequences in primary cells and cell lines. We characterized a set of cis-acting elements within the CFTR locus and demonstrated direct physical interaction between them and the CFTR promoter, by chromosome conformation capture (3C). These results provide the first insight into the three-dimensional structure of the active CFTR gene. Current projects are aimed at characterizing the mechanism of action of the cis-acting elements and the proteins that coordinate their function. We are also taking whole genome approaches to define transcriptional networks that coordinate differentiated functions in human epithelia.
Pancreas Cancer:
The normal health of all epithelial surfaces in the human body is dependent on the presence of a surface layer of adequately hydrated mucus. The major protein components of this mucus layer are mucus glycoproteins, mucins, which may either be attached to the cell membrane or secreted from the epithelial surface. The normal functions of mucin glycoproteins may be usurped by cancer cells. We are dissecting the biological properties of an abundant secreted mucus glycoprotein, MUC6, that is found at several organ sites, including the pancreas, but about which very little is currently known. We are evaluating the hypothesis that MUC6 functions in the normal pancreatic duct to maintain epithelial integrity, protect the epithelium from environmental insults and contribute to the repair of epithelial damage. However, in the early stages of pancreatic cancer, aberrant expression of MUC6 may contribute to progression of this devastating disease.
Collagen XV is a proteoglycan found in the basement membrane zones of a number of tissues but its precise functions remain to be elucidated. Our published data on cervical cancer epithelial cells support the hypothesis that human collagen XV is a dose-dependent suppressor of tumorigenicity. We predict that the hypothesis will be applicable to other epithelial tumors and are currently testing our hypothesis in the epithelium of the pancreatic duct.
Selected Recent Publications
Ott C.J., Bischof J.M., Unti K.M., Gillen A.E., Leir S.H., and Harris A. (2011) Nucleosome occupancy reveals regulatory elements of the CFTR promoter. Nucleic Acids Res. Sep 24 (Epub ahead of print).
* Bischof, J.M., Ott, C.J., Leir, S.H., Gosalia, N., Song, L., London, D., Furey, T.S., Cotton, C.U., Crawford, G.E., Harris, A. (2011) A genome-wide analysis of open chromatin in human tracheal epithelial cells reveals novel candidate regulatory elements for lung function. Thorax. In Press.
* Guo, X.L., Pace, R.G., Stonebraker, J.R., Commander, C.W., Dang A.T., Drumm, M.L., Harris, A., Zou F., Swallow, D.M., Wright, F.A., O'Neal, W.K., Knowles M.R. (2011) Mucin variable number tandem repeat polymorphisms and severity of cystic fibrosis lung disease: significant association with MUC5AC. PLoS One. Oct.: 6(10).
Zhang Z, Ott C.J., Lewandowska M.A., Leir S.H., Harris A. (2011) Molecular mechanisms controlling CFTR gene expression in the airway. J Cell Mol Med. Sep 2 (Epub ahead of print).
Leir, S.H., Harris, A. (2011) MUC6 mucin expression inhibits tumor cell invasion. Experimental Cell Research; 317: 2408-2419.
Gillen A.E., Gosalia N., Leir S.H., and Harris A. (2011) microRNA regulation of expression of the cystic fibrosis transmembrane conductance regulator gene. Biochem. J. 438: 25-32.
Lewandowska M.A., Costa F., Bischof J.M., Williams S.H., Soares M.B., and Harris, A. (2010) Multiple mechanisms influence regulation of the cystic fibrosis transmembrane conductance regulator gene promoter. Am J. Respir Cell Mol Bio. 43(3): 334-41.
Ott C.J., Blackledge N.P., Leir S.H., Harris A. (2009) Novel regulatory mechanisms for the CFTR gene. Biochem. Soc. Trans. 37:843-8.
Blackledge N.P., Ott C.J., Gillen A.E., Harris A. (2009) An insulator element 3' to the CFTR gene binds CTCF and reveals an active chromatin hub in primary cells. Nucleic Acids Res. March;37(4): 1086-94.
Ott C., Suszko M., Blackledge N.P., Wright J.E., Crawford G.E., Harris A. (2009) A complex intronic enhancer regulates expression of the CFTR gene by direct interaction with the promoter. J. Cell and Mol. Med. Apr;13(4):680-92.
Kotzamanis G., Abdulrazzak H., Gifford-Garner J., Haussecker P.L., Cheung W., Harris A., Kotsinas A., Gorgoulis V., Huxley C. (2008) CFTR expression from a BAC carrying the complete human gene and associated regulatory elements. J. Cell and Mol. Med. (in press)
Evans J.R., Kelly D.L., Morris K.J., Arvide E.M., Harris A. (2008) RNA interference-mediated inhibition of hepatocyte nuclear factor 1alpha identifies target genes. Biochemica et Biophysica Acta May; 1779(5); 341-6.
Harris A., Harris H., Hollingsworth M.A. (2007) Complete suppression of tumor formation by high levels of basement membrane collagen. Mol Cancer Research 5(12): 1241-5.
Blackledge N.P., Carter E.J., Evans J.R., Lawson V., Rowntree R.K., Harris A. (2007) CTCF mediates insulator function at the CFTR locus. Biochem J. Dec 1; 408(2): 267-75.