Susan M. Janicki, Ph.D.
Assistant Professor, Gene Expression and Regulation Program

Genetics and Gene Regulation

Address

The Wistar Institute
3601 Spruce Street
Philadelphia, PA 19104-6069

Office tel.: 215-495-6850
Lab tel.: 215-495-6851
Fax: 215-495-6849
E-mail: sjanicki@wistar.org

Tufts Universtity, BS (Biology), 1993

University of Maryland, Baltimore, Ph.D. (Human Genetics), 1999

Postdoctoral research, Cold Spring Harbor Laboratory, 2005

Other Links

Dr. Janicki's Wistar Page

Research Interests

• Live cell analysis of epigenetic regulatory mechanisms.

Key words: live cell imaging, gene expression, chromatin organization, epigenetics, nuclear organization

Search PubMed for articles

Description of Research

Genes are transcribed, not from naked DNA, but from chromatin - the packaged form of DNA in the nucleus. Therefore, the processes required for gene expression must be coordinately regulated at chromatin templates, and chromatin organization plays a central role in regulating these events. To decipher the intricacies of these important regulatory processes, we have developed an innovative imaging system that permits real-time analysis of gene expression events at chromatin in single living cells. This system combines high affinity bacterial DNA/protein and bacteriophage RNA/protein interaction units with Green Fluorescent Protein (GFP) to permit the simultaneous visualization of the three key macromolecules in gene expression - DNA, RNA, and proteins. When these sequence elements are introduced into eukaryotic cells, and their binding proteins expressed as GFP fusion proteins, it is possible to correlate changes in chromatin organization with changes in RNA and regulatory factor levels at the site of transcription. Our approach is a significant advance on current methods, which provide static portraits of cellular activity, as it provides a dynamic picture of unperturbed gene regulation in single living cells. Using this system, we have observed transcriptionally silent heterochromatin being transformed into transcriptionally active euchromatin, and visualized the recruitment and displacement of regulatory proteins during this transition. As we can now observe the dynamics of gene regulatory process in single living cells, these studies will allow us to delineate the signaling cascades that regulate gene expression at the "the site of action" - chromatin - and they could reveal new regulatory paradigms that will have implications for the treatment of human diseases.

Although technically sophisticated, imaging nucleic acids in single living cells has the potential to become not only a standard signal transduction assay with which to identify factors that interact in a novel and/or transient way with chromatin, but it can also be used to define the temporal and spatial dynamics of these processes. Using our system, we are currently investigating mechanisms of RNA-mediated chromatin regulation, DNA demethylation, and histone variant exchange. As we are able to directly visualize chromatin regulatory events over time in single living cells, this technology will allow us to discover regulatory mechanisms that would be impossible to imagine outside of the in vivo environment.

Recent Publications

Janicki SM, Tsukamoto T, Salghetti SE, Tansey WP, Sachidanandam R, Prasanth KV, Ried T, Shav-Tal Y, Bertrand E, Singer RH, Spector DL. (2004) From Silencing to Gene Expression: Real-Time Analysis in Single Cells. Cell 116, 683-698.

Shav-Tal Y, Darzacq X, Shenoy SM, Fusco D, Janicki SM, Spector DL, Singer RH. (2004) Dynamics of Single mRNPs in the Nuclei of Living Cells. Science 18, 1797-1800.

Rafalska-Metcalf IU and Janicki SM. (2007) Show and Tell: Visualizing Gene Expression in Living Cells. Journal of Cell Science, 120, 2301-7.

Lab

Rotation Projects

1. Investigate mechanisms of DNA demethylation by analyzing the recruitment of DNA glycosylases to a region of heterochromatin during transcriptional activation
   
   
2. Analyze the kinetics of mRNA synthesis and processing at a transcription site in a single living cell in order to understand the control points of gene expression.
   
   
3. Screen candidate chromatin regulatory factors, tagged with yellow fluorescent protein (YFP), for recruitment to a region of heterochromatin during transcriptional activation in order to identify new epigenetic regulatory mechanisms
   
   
4. Discuss other potential projects with Susan Janicki.
   

Lab Personnel:

Lucy Joo - Research Assistant
Ilona Rafalska-Metcalf - Postdoctoral Fellow
Sara Powers - Postdoctoral Fellow