The unfolded protein response (UPR), a well-known adaptive mechanism for cells to maintain ER homeostasis, has been implicated in the pathogenesis of a variety of human diseases. Genetic deletion of the UPR signaling components can significantly influence the disease progression in mouse models for diabetes, hepatic steatosis, IBD, ALS and other diseases. We have recently performed a synthetic biology screen to interrogate the mammalian UPR pathway. From this screen, we have identified RtcB as a long sought RNA ligase that catalyzes unconventional XBP-1 splicing during ER stress. RtcB is a multifunctional RNA ligase that also acts in tRNA splicing. Genetic rescue of RtcB knockout cells suggests that RtcB-mediated ligation of XBP1 and tRNA may occur at different subcellular compartments. We will therefore determine subcellular compartment-specific RtcB function. By generating Trpt1 and RtcB double knockout cells and performing genetic rescue, we further demonstrate that a second biochemically distinct RNA ligation pathway cooperates with RtcB in mammalian cells to regulate XBP1 and tRNA splicing. Therefore, we will examine the role of other putative components in the RNA ligation pathway. Lastly we will identify unknown RNA ligases of the new ligation pathway by a genetic suppressor screen using RtcB knockout cells. By revealing the complete molecular repertoire of RNA ligation pathways, we will hopefully gain new insights and uncover new therapeutic targets to modulate the mammalian UPR.

Public Health Relevance

The Unfolded Protein Response (UPR) plays key roles in a variety of pathological processes; however, RNA ligation, a key step of mammalian UPR, has not been well characterized. We propose to investigate how two biochemically distinct RNA ligation pathways act in concert to regulate the output of UPR. Better understanding of this regulatory mechanism is crucial for designing therapeutic strategies to modulate cellular stress response.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM120307-03
Application #
9731575
Study Section
Membrane Biology and Protein Processing Study Section (MBPP)
Program Officer
Ainsztein, Alexandra M
Project Start
2017-09-30
Project End
2021-06-30
Budget Start
2019-07-01
Budget End
2020-06-30
Support Year
3
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Northwestern University at Chicago
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
160079455
City
Chicago
State
IL
Country
United States
Zip Code
60611