Christopher Nicchitta, Ph.D. (University of Pennsylvania)
Professor, Department of Cell Biology
Associate Dean for Research Training
CMB Program, Comprehensive Cancer Center
436A Nanaline Duke Bldg., Box 3709
Duke University Medical Center
Durham, NC 27710
Our laboratory studies the cellular architecture and regulation of protein synthesis, with the goal of understanding how cells regulate the subcellular organization and temporal dynamics of protein synthesis. We focus on mRNA localization - the process by which cells control where and when a protein is synthesized by localizing its mRNA to a discrete location(s) in the cell. Such regulation is critical for many aspects of cell dynamics, cell signaling and cell division. Of the diverse mRNA localization phenomena that have been identified to date, the most prominent is mRNA localization to the endoplasmic reticulum (ER). mRNA localization to the ER operates on an unusually large scale (essentially the entire mRNA transcriptome is partially represented on the ER, with those mRNAs encoding secretory and membrane proteins being highly ER-enriched), and continuously– all newly exported mRNAs undergo selection for translation in the cytosol and/or the ER compartments.
We use a broad array of experimental approaches - biochemistry, cell biology, genomics, and computational biology - and are focusing on several related themes. First, we are working to identify the mRNA-encoded signals used to target mRNAs to the ER as well as the cellular factors that recognize these signals. One mechanism, in which a signal in nascent secretory and membrane proteins directs mRNA recruitment to the ER, has been previously described. It is clear though that there are multiple pathways that direct mRNAs to the ER, including pathways that direct cytosolic and nucleoplasmic protein-encoding mRNAs to the ER. We are also investigating how, once localized, mRNAs are anchored to the ER membrane. In a recent study, we reported that the cohort of mRNAs encoding organelle resident proteins(e.g., nuclear envelope, ER, Golgi, lysosomes, peroxisomes) are localized tothe ER and directly anchored to components of the ER membrane. We are very interested in understanding what anchoring signals and anchoring signal binding protein(s) mediate this process and how direct mRNA anchoring contributes to cell structure and function.
In parallel efforts, we discovered that mRNA translation is under distinct regulatory control in the cytosol and ER compartments, with translation being 3-5 fold more efficient on the ER. These differences are substantial and suggest that mRNA localization to the ER may represent an important post-transcriptional gene expression mechanism. To gain insight into the mechanisms and factors responsible for the compartmental regulation of mRNA translation we are using traditional biochemical approaches (pulse-labeling, cell fractionation, immunoprecipitation, proteomics) as well as genomic approaches (ribosome footprinting, deep sequencing).
Garcia-Blanco MA, Vasudevan SG, Bradrick SS, Nicchitta C. (2016) Flavivirus RNA transactions from viral entry to genome replication. Antiviral Res. 134:244-249.
Reid DW, Tay AS, Sundaram JR, Lee IC, Chen Q, George SE, Nicchitta CV, Shenolikar S. (2016) Complementary roles of GADD34- and CReP-containing eIF2α Phosphatases during the Unfolded Protein Response. Mol Cell Biol (Epub ahead of print)
LaMonte G, Walzer KA, Lacsina J, Nicchitta C, Chi JT. (2015) Methods to Investigate the Regulatory Role of Small RNAs and Ribosomal Occupancy of Plasmodium falciparum. J Vis Exp. 4;(106):e53214.
Reid DW, Shenolikar S, Nicchitta CV. (2015) Simple and inexpensive ribosome profiling analysis of mRNA translation. Methods. pii: S1046-2023(15)30017-7.
Reid DW, Nicchitta CV. (2015) LOCAL TRANSLATION. Comment on "Principles of ER cotranslational translocation revealed by proximity-specific ribosome profiling". Science. 348(6240):1217.
Reid DW, Nicchitta CV. (2015) Diversity and selectivity in mRNA translation on the endoplasmic reticulum. Nat Rev Mol Cell Biol. 16(4):221-31
Brooks SS, Wall AL, Golzio C, Reid DW, Kondyles A, Willer JR, Botti C, Nicchitta CV, Katsanis N, Davis EE. (2014) A novel ribosomopathy caused by dysfunction of RPL10 disrupts neurodevelopment and causes X-linked microcephaly in humans. Genetics. 198(2):723-33.
Reid DW, Chen Q, Tay AS, Shenolikar S, Nicchitta CV. (2014) The unfolded protein response triggers selective mRNA release from the endoplasmic reticulum. Cell. 158(6):1362-74.
Jagannathan S, Reid DW, Cox AH, Nicchitta CV. (2014) De novo translation initiation on membrane-bound ribosomes as a mechanism for localization of cytosolic protein mRNAs to the endoplasmic reticulum. RNA. 20(10):1489-98.
Jagannathan S, Hsu JC, Reid DW, Chen Q, Thompson WJ, Moseley AM, Nicchitta CV. (2014) Multifunctional roles for the protein translocation machinery in RNA anchoring to the endoplasmic reticulum. J Biol Chem. 289(37):25907-24.