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Factors that determine cell-specific gene expression in pancreatic endocrine tumor cells
J F Habener1, M Vallejo, J P Hoeffler
1Laboratory of Molecular Endocrinology, Massachusetts General Hospital, Harvard Medical School, Boston.
Abstract:
Phenotypically distinct islet tumor cell lines may recapitulate certain of the developmental pathways of normal islet cell differentiation by expressing a combinatorial set of positively and negatively acting DNA-binding proteins to allow for the programmed expression of genes encoding polypeptide hormones. The structure of one of these DNA-binding proteins, a cyclic AMP-responsive protein (CREB) that binds specific DNA regulatory elements in the somatostatin gene, has been deduced from the sequence of a cloned cDNA. The CREB protein contains a DNA-binding domain separate from a cAMP-dependent protein kinase A activation domain. Further characterizations of the genes encoding the DNA-binding proteins should help to elucidate the cellular processes involved in islet cell differentiation and the genesis of tumors.
Insights
Islet tumor cells may mimic normal cell development by using DNA-binding proteins to control gene expression. Researchers characterized cyclic AMP-responsive element-binding protein (CREB), crucial for somatostatin gene regulation.
Area of Science:
- Molecular endocrinology
- Cancer biology
- Cellular differentiation
Background:
- Islet tumor cells can model normal islet cell differentiation pathways.
- Gene expression in these cells is regulated by DNA-binding proteins.
- Understanding these proteins is key to understanding islet cell development and tumorigenesis.
Purpose of the Study:
- To investigate the role of DNA-binding proteins in islet cell differentiation.
- To characterize the structure and function of cyclic AMP-responsive element-binding protein (CREB) in the context of islet cell tumors.
- To explore the implications for understanding islet cell tumors and differentiation.
Main Methods:
- Cloning of complementary DNA (cDNA) encoding CREB.
- Deduction of CREB protein structure from cDNA sequence.
- Analysis of CREB's DNA-binding and activation domains.
Main Results:
- The structure of CREB, a cyclic AMP-responsive DNA-binding protein, was determined.
- CREB binds to specific DNA regulatory elements within the somatostatin gene.
- CREB possesses a distinct DNA-binding domain and a cAMP-dependent protein kinase A activation domain.
Conclusions:
- Phenotypically distinct islet tumor cell lines offer insights into normal islet cell differentiation.
- CREB is a key regulatory protein involved in somatostatin gene expression.
- Further study of genes encoding DNA-binding proteins will illuminate islet cell differentiation and tumor formation.