Many proteins involved in gene expression contain a low complexity domain that itself lacks secondary structure but which can form intermolecular polymers known as amyloid, a stable structure that can organize into filaments and hydrogels. Some of the proteins that bear such intrinsically unstructured domains interact with RNA polymerase II or the RNA produced during transcription. Indeed, this structural feature is unusually over-represented in cellular RNA- binding proteins. A current hypothesis suggests that these low complexity domains are proteinaceous switches that, with their adjacent folded portions such as RNA recognition motifs, assemble into cellular compartments that handle and process RNA. Excellent examples include yeast Nab3 and Nrd1 which are factors needed for termination of short transcripts such as snRNAs and snoRNAs. Similarly, potential amyloid forming domains that couple mRNA polyadenylation to termination at the end of protein coding genes are seen in Pcf11, Hrp1, and Rat1. Low complexity self-assembling domains are causally implicated in human diseases, particularly neurodegenerative pathologies in which aberrant cellular inclusions are a common characteristic. A leading model is that the normal propensity for aggregation of RNA-binding proteins can go awry, leading to toxic oligomeric and polymeric assemblies that are associated with cellular damage. Yet we have a poor understanding of the normal reversible function of these domains and why their aggregation can become toxic. The long-term goal of the project is to understand what amyloid forming domains provide for the function of RNA binding proteins; particularly those involved in terminating transcription of RNA polymerase II. The working hypothesis is that conditional polymerization of these proteins is a key part of how they operate. One model is that these proteins enshroud nascent RNA in a specific manner for presentation to the enzymes of termination and processing such as helicases and nucleases; perhaps in the way nucleosomes package DNA. The focus of this work is on RNA- binding, transcription termination factors in yeast where their involvement in the termination of transcription is fairly well understood. All possess low complexity domains that can potentially oligomerize. The prototype is the yeast hnRNP-like protein Nab3 that bears a polyglutamine-rich, self-assembly domain essential for cell viability and important for transcription termination. This project tests the role of these domains in the transcription termination machinery with respect to: 1) their amyloid forming potential, 2) the need for them for cell viability, and 3) their requirement for termination. Success in these aims will lead to new mechanistic models of how these RNA-protein interactions lead to productive and accurate gene expression.

Public Health Relevance

. Neurodegenerative diseases are a major public health problem, particularly as the American population ages. Many neurodegenerative diseases share a common basis; they result from the derangement of proteins involved in RNA metabolism resulting in the loss of their normal operation as part of RNA-protein complexes. This project will examine the fundamental mechanisms by which this class of proteins and their RNA partners function.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM120271-02
Application #
9335978
Study Section
Molecular Genetics B Study Section (MGB)
Program Officer
Sledjeski, Darren D
Project Start
2016-09-01
Project End
2020-05-31
Budget Start
2017-06-01
Budget End
2018-05-31
Support Year
2
Fiscal Year
2017
Total Cost
$325,056
Indirect Cost
$115,056
Name
Emory University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Loya, Travis J; O'Rourke, Thomas W; Reines, Daniel (2017) The hnRNP-like Nab3 termination factor can employ heterologous prion-like domains in place of its own essential low complexity domain. PLoS One 12:e0186187
Loya, Travis J; Reines, Daniel (2016) Recent advances in understanding transcription termination by RNA polymerase II. F1000Res 5:
O'Rourke, Thomas W; Reines, Daniel (2016) Determinants of Amyloid Formation for the Yeast Termination Factor Nab3. PLoS One 11:e0150865
Arndt, Karen M; Reines, Daniel (2015) Termination of Transcription of Short Noncoding RNAs by RNA Polymerase II. Annu Rev Biochem 84:381-404