The precise control of cell differentiation and proliferation is mediated by the interaction of extracellular growth factors with discrete membrane receptors. Transduction of the surface signal to the various cellular compartments, including the nucleus, is mediated by a phosphorylation cascade of intracellular substrates, culminating in the activation of specific transcription factors. Because p21ras functions as the critical switch which converts a receptor tyrosine kinase signal initiated at the membrane into a serine/threonine kinase cascade, p21ras expression vectors have been used to analyze growth factor-induced responses. Typically, p21ras-induced protein phosphorylation has been assayed. However, the functional consequence of such modifications, and whether these modification are common to all cell types, irrespective of their developmental history, remains ill-defined. Therefore, defining the precise molecular mechanisms by which growth factor/ras-induced signaling pathways common to all cell types result in cell-specific responses, remains a fundamental problem in current biology. To this end, we have developed a transient co-transfection approach in cultured GH4 rat pituitary cells to test the effects of oncogenic V-12 ras on the promoter activity of a cellular gene whose expression is highly restricted to the pituitary cell type: rat prolactin (rPRL). Using this assay, we have shown that V-12 ras selectively and significantly activities the rPRL promoter, and we have identified and ordered the functional components of the ras signaling cascade, from the membrane to the nucleus, as: ras raf kinase MAP kinase ets-1/GHF-1. Further studies have shown that a ras-dependent functional interaction of the ubiquitous nuclear proto- oncogene transcription factor, ets-1, with the pituitary-specific transcription factor, GHF-1/Pit-1, is required for the synergistic enhancement of the oncogene-mediated activation of the rPRL promoter; whereas neither factor alone is sufficient to mediate this response. Moreover, we have mapped the ras responsive element (RRE) of the rPRL promoter to a DNA region which contains both a putative ets site and an adjacent GHF-1/Pit-1 site. Thus, we have discovered that a ras- dependent, functional interaction of these two factors confers a pituitary-specific response to the general ras signaling pathway. Based on these preliminary results, the long-term goal of the current proposal is to show that the molecular mechanism by which the ras signaling cascade governs pituitary-specific gene expression is via a signal- activated and phosphorylation-dependent interaction of ets-1 with GHF-1, resulting in a more stable ets-1/GHF-1 transcription factor complex on the rPRL RRE.
The specific aims to accomplish this goal are: (1) to fine-map the precise DNA sequences of the rPRL ras responsive element; (2) to determine whether ets-1 and GHF-1 physically interact; (3) to map the ras-mediated phosphorylation site(s) on ets-1 and/or GHF-1; and, (4) to map the ras-dependent, functionally-interactive domains of ets-1 and GHF-1. Our discovery not only has important scientific implications regarding the molecular mechanisms by which generic signal are harnessed for the control of cell-specific processes, but also provides novel insights into the molecular mechanisms by which pituitary tumors might arise.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK046868-02
Application #
2146135
Study Section
Endocrinology Study Section (END)
Project Start
1994-06-01
Project End
1999-05-31
Budget Start
1995-06-01
Budget End
1996-05-31
Support Year
2
Fiscal Year
1995
Total Cost
Indirect Cost
Name
University of Colorado Denver
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
065391526
City
Aurora
State
CO
Country
United States
Zip Code
80045
Roof, Allyson K; Trudeau, Tammy; Gutierrez-Hartmann, Arthur (2018) Pituitary somatolactotropes evade an oncogenic response to Ras. Mol Cell Endocrinol 476:165-172
Roof, Allyson K; Jirawatnotai, Siwanon; Trudeau, Tammy et al. (2018) The Balance of PI3K and ERK Signaling Is Dysregulated in Prolactinoma and Modulated by Dopamine. Endocrinology 159:2421-2434
Booth, Allyson; Trudeau, Tammy; Gomez, Crystal et al. (2014) Persistent ERK/MAPK activation promotes lactotrope differentiation and diminishes tumorigenic phenotype. Mol Endocrinol 28:1999-2011
Jean, Annie; Gutierrez-Hartmann, Arthur; Duval, Dawn L (2010) A Pit-1 threonine 220 phosphomimic reduces binding to monomeric DNA sites to inhibit Ras and estrogen stimulation of the prolactin gene promoter. Mol Endocrinol 24:91-103
Jedlicka, Paul; Sui, Xiaomei; Gutierrez-Hartmann, Arthur (2009) The Ets dominant repressor En/Erm enhances intestinal epithelial tumorigenesis in ApcMin mice. BMC Cancer 9:197
Jedlicka, Paul; Sui, Xiaomei; Sussel, Lori et al. (2009) Ets transcription factors control epithelial maturation and transit and crypt-villus morphogenesis in the mammalian intestine. Am J Pathol 174:1280-90
Gutierrez-Hartmann, Arthur; Duval, Dawn L; Bradford, Andrew P (2007) ETS transcription factors in endocrine systems. Trends Endocrinol Metab 18:150-8
Ferry, A L; Locasto, D M; Meszaros, L B et al. (2005) Pit-1beta reduces transcription and CREB-binding protein recruitment in a DNA context-dependent manner. J Endocrinol 185:173-85
Schweppe, Rebecca E; Melton, Alexis A; Brodsky, Kelley S et al. (2003) Purification and mass spectrometric identification of GA-binding protein (GABP) as the functional pituitary Ets factor binding to the basal transcription element of the prolactin promoter. J Biol Chem 278:16863-72
Duval, Dawn L; Jean, Annie; Gutierrez-Hartmann, Arthur (2003) Ras signaling and transcriptional synergy at a flexible Ets-1/Pit-1 composite DNA element is defined by the assembly of selective activation domains. J Biol Chem 278:39684-96

Showing the most recent 10 out of 22 publications