Professor, Full Member of Indiana University Graduate Faculty Department of Cellular & Integrative Physiology Indiana University School of Medicine  635 Barnhill Drive, Room 333 Indianapolis, Indiana 46202-5120 E-mail: rnday @ iupui.edu Phone: 317-274-2166 Fax: 317-274-3318

Education / Training

• 1978, B.S., University of Colorado, Boulder, CO
• 1980, M.S., State University of NY, Fredonia, NY
• 1987, Ph.D., University of Rochester, Rochester, NY
• 1990, Postdoctoral Fellowship, University of Iowa, Iowa City, IA

Research

Cell-Type Specific Regulation of Pituitary Gene Expression

The initiation of programs of gene expression in differentiated cells requires the interactions between cell-type specific transcription factors, nuclear receptors, and coregulatory proteins that occur in the cell nucleus. The focus of our research is to determine how tissue-specific transcription factors in cells of the anterior pituitary regulate the assembly of the protein complexes that control pituitary gene expression. Our studies are showing how Pit-1, a pituitary specific homeodomain transcription factor, orchestrates the activities of a network of transcription factors and co-regulatory proteins that function to control prolactin and growth hormone gene expression.

The Organization of Nuclear Function

Using biochemical and molecular genetic approaches, we are determining how Pit-1 coordinates this network of protein interactions. For example, we showed that Pit-1 and the transcription factor C/EBPα cooperate in the activation of pituitary cell-specific gene transcription. Interestingly, our studies also revealed that C/EBPα was preferentially localized to regions of centromeric heterochromatin in mouse pituitary cells - regions of the genome typically associated with gene silencing. Our current studies are focused on determining how the protein interactions that are coordinated by Pit-1 function to remodel densely packaged chromatin, allowing the access of the pituitary-specific transcription factors to target genes. These biochemical and molecular genetic studies, however, are not enough to provide a complete picture of the mechanisms that control transcription.

Imaging Transcription Factor Interactions in Living Cells?

Proteins are in dynamic equilibrium inside the cell, and it is necessary to understand the mechanisms that control the assembly of regulatory protein complexes in the context of their natural environment. To address this, we are using advanced live-cell imaging methods to track the behavior of proteins within the organized microenvironment of the living cell. For example, we used the direct visualization of fluorescent protein-labeled Pit-1 and C/EBPα in living pituitary cells to demonstrate that Pit-1 recruited C/EBPα from the regions of centromeric heterochromatin to the intranuclear sites occupied by Pit-1. These studies are showing how the network interactions of nuclear proteins lead to the formation of dynamic complexes, which in turn are stabilized by interactions with chromatin. What is more, this approach has allowed us to demonstrate how disease-causing mutations in Pit-1 disrupt the network of protein interactions. These results have broad implications for many human diseases that have been linked to mutations in the homeodomain proteins. This analysis of protein interaction networks in their natural environment will be the key to understanding the control of gene expression at the structural level.

Grant Funding: NIH-NIDDK

Selected Publications

Day RN, Schaufele F. 2005.  Imaging molecular interactions in living cells.
Molecular Endocrinology 19: 1675-1686.

Voss TC, Demarco IA, Booker CF, Day RN. 2005.  Functional Interactions with Pit-1 Reorganize Corepressor Complexes within the Nucleus.
J Cell Science 118: 3277-3288.

Demarco IA, Periasamy A, Booker CF, Day RN. 2006.  Monitoring Dynamic Protein Interactions with Photo-quenching FRET.
Nature Methods 3(7): 519-524.

Demarco IA, Voss TC, Booker CF, Day RN. 2006.  Dynamic Interactions between Pit-1 and C/EBP alpha in the Pituitary Cell Nucleus.
Molecular and Cellular Biology 26: 8087-8098.

Chen Y, Mauldin JP, Day RN, Periasamy, A. 2007.  Characterization of spectral FRET imaging microscopy for monitoring the nuclear protein interactions.
Journal of Microscopy 228: 139-152.

Day RN, Booker CF, Periasamy, A. 2008.  The characterization of an improved donor fluorescent protein for Förster resonance energy transfer microscopy.
Journal of Biomedical Optics 13(3): 31203.

PubMed Listings for this Faculty Member 

Day Laboratory Home Page

Last update: 11/19/2008