Document text
Principal Investigator: Esteban Daniel Erben
Organization: RBHS-NEW JERSEY MEDICAL SCHOOL
Fiscal Year: 2021
Award: $198,750
Funding agency: National Institute of Allergy and Infectious Diseases
PROJECT SUMMARY
Trypanosoma brucei causes African trypanosomiasis in humans and livestock. In the mammalian infectious
Bloodstream-Form (BF) stage, T. brucei expresses a single species of Variant Surface Glycoprotein (VSG)
genes from over 2,500 VSG repertoire with a potential of switching to a different VSG gene, a phenomenon
known as antigenic variation. This allows the parasite to escape from the action of the host immune system and
leads to a chronic infection. The surface of a BF trypanosome cell is coated with about 11 million VSG proteins,
which can be translated from about 1,400 copies of VSG mRNA (about 7% of total mRNA). Because VSG is
essential for the viability of BF T. brucei, the parasites must maintain the functional high level of VSG mRNA and
VSG protein to survive. Almost all genes are transcribed polycistronically in T. brucei, including VSG. One way
to achieve the high level of VSG mRNA is through transcription. A single VSG allele is expressed from the
transcriptionally active ‘BF Expression Site (BES)’, a Polycitronic Transcription Unit (PTU), containing an RNA
pol I promoter, several of Expression-Site Associated Genes (ESAGs) and a VSG. About 15 BESs are present
but only one is transcriptionally active and the remaining BESs are repressed. Although high levels of ESAGs
and VSG transcripts are produced from the active BES, the abundance differs significantly, with VSG transcripts
100~1000-fold higher than ESAGs. This suggests that there must be trans-acting VSG mRNA specific regulators,
most probably RNA-binding proteins (RBPs) that maintain the high level of VSG mRNA. Additionally, VSG is
expressed during BF stage but not in other stages of life-cycle during T. brucei differentiation. Despite the
importance, almost nothing is known about mechanisms for post-transcriptional regulation of VSG mRNA, except
that a short, conserved sequence element embedded into the 3´UTR of VSG mRNA (16-mer) confers both stage
specificity and stability. Here we hypothesize that the 3´UTR of VSG mRNA have sequence-specific binding
sites for RBPs and that the assembly and composition of this VSG mRNA RiboNucleoprotein Particles, ‘VSG
mRNPs’, promote translation and/or protect VSG mRNA from degradation, maintaining the vast amount of VSG
mRNA and thus, protein also. In this proposal we aim to identify the components of VSG mRNPs in BF T. brucei.
We will first genetically and biochemically identify the components of the VSG mRNP complex in Aim 1 and
validate potential candidates in Aim 2. VSG serves multiple roles in the survival of BF trypanosome; it can protect
the parasite but can also trigger strong adaptive host immune response. Even though VSG is a strong antigen,
developing vaccine therapy for African trypanosomiasis has been difficult due to the antigenic variation. Given
that VSG is absolutely essential for BF T. brucei, understanding the VSG expression control mechanisms
(specifically how RBPs impact on functions of VSG mRNPs) would not only enable us to discover fundamental
biology of T. brucei gene expression but also to discover a new biology that could lead to therapeutic intervention
of this human disease.
!
!
Terms: <Actins><Affect><African Sleeping Sickness><African Trypanosomiasis><Alleles><Allelomorphs><Antigen Variation><Antigenic Variability><Antigenic Variation><Antigens><Area><Assay><Autoregulation><B blood cells><B cell><B cells><B-Cells><B-Lymphocytes><B-cell><Binding><Binding Proteins><Binding Sites><Bioassay><Biochemical><Biologic Assays><Biologic Models><Biological Assay><Biological Models><Biology><Blood Circulation><Bloodstream><Catalogs><Categories><Cell Body><Cell Cycle><Cell Division Cycle><Cell Surface Antigens><Cell Surface Glycoproteins><Cell Survival><Cell Viability><Cells><Circulation><Combining Site><Complex><Consequentialism><Conserved Sequence><DNA Polymerase I><DNA Polymerase alpha><DNA-Dependent DNA Polymerase I><Data Set><Dataset><Development><Disease><Disorder><Elements><Farm Animal><Flow Cytofluorometries><Flow Cytofluorometry><Flow Cytometry><Flow Microfluorimetry><Flow Microfluorometry><Gene Action Regulation><Gene Expression><Gene Expression Regulation><Gene Regulation><Gene Regulation Process><Gene Transcription><Gene variant><Genes><Genetic><Genetic Alteration><Genetic Change><Genetic Transcription><Genetic Translation><Genetic defect><Half-Life><High-Throughput Nucleotide Sequencing><High-Throughput Sequencing><Homeostasis><Human><Immune Globulins><Immune response><Immune system><Immunoglobulins><Immunologic Surface Markers><Immunological Surface Markers><Immunological response><Klenow Fragment><Lead><Libraries><Life Cycle><Life Cycle Stages><Ligand Binding Protein><Ligand Binding Protein Gene><Livestock><Maintenance><Mass Photometry/Spectrum Analysis><Mass Spectrometry><Mass Spectroscopy><Mass Spectrum><Mass Spectrum Analyses><Mass Spectrum Analysis><Membrane Glycoproteins><Messenger RNA><Model System><Modern Man><Molecular Interaction><Mutation><Non-Polyadenylated RNA><ORFs><Open Reading Frames><Outcome><Parasites><Pb element><Physiological Homeostasis><Pol I><Population><Post-Transcriptional Control><Post-Transcriptional Gene Silencing><Post-Transcriptional Regulation><Posttranscriptional Gene Silencing><Protein Binding><Protein Coding Region><Protein Overexpression><Proteins><Proteome><Publishing><Quelling><RNA><RNA Binding><RNA Expression><RNA Gene Products><RNA Interference><RNA Silencing><RNA bound><RNA interference screen><RNA-Binding Proteins><RNAi><RNAi screen><RNAi-based screen><Reactive Site><Regulation><Reporter><Research><Ribonucleic Acid><Ribonucleoproteins><Role><Sequence-Specific Posttranscriptional Gene Silencing><Site><Specificity><Surface><Surface Antigens><Surface Glycoproteins><System><T brucei><T. brucei><Testing><Therapeutic Intervention><Transcript><Transcription><Translating><Translations><Trypanosoma><Trypanosoma brucei><Trypanosoma brucei brucei><Trypanosome><VAC-TX><Vaccine Therapy><Variant><Variation><allele variant><allelic variant><allergic/immunologic body system><allergic/immunologic organ system><bound protein><candidate validation><catalog><chronic infection><developmental><effective therapy><effective treatment><experiment><experimental research><experimental study><flow cytophotometry><genetic approach><genetic strategy><genetic variant><genome mutation><genomic variant><heavy metal Pb><heavy metal lead><host response><human disease><human pathogen><immune system response><immunogen><immunoresponse><insight><intervention therapy><life course><mRNA><mRNA Degradation><mRNA Stability><mRNA Transcript Degradation><mRNA Translation><mRNP><messenger ribonucleoprotein><neglect><new therapeutic approach><new therapeutic intervention><new therapeutic strategies><new therapy approaches><novel><novel therapeutic approach><novel therapeutic intervention><novel therapeutic strategies><novel therapy approach><overexpress><overexpression><particle><persistent infection><post-transcriptional gene regulation><posttranscriptional control><posttranscriptional regulation><promoter><promotor><protein complex><sleeping sickness><social role><therapeutic vaccination><tool>