Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


MA-Dissertation-6-19-22.pdf (35.35 MB)

ETD Abstract Container

Abstract Header

Functions of Trypanosoma brucei RAP1 in Antigenic Variation

Afrin, Marjia
http://orcid.org/0000-0002-7730-7516
http://rave.ohiolink.edu/etdc/view?acc_num=csu1655616654470721

Abstract Details

2022, Doctor of Philosophy in Regulatory Biology, Cleveland State University, College of Sciences and Health Professions.
Trypanosoma brucei (T. brucei) causes sleeping sickness in humans and regularly switches its major surface antigen, variant surface glycoprotein (VSG), to evade the host immune response. TbRAP1, a telomere protein, is essential for VSG silencing, suppresses the level of telomeric repeat containing RNA (TERRA) and the telomeric R-loop, and suppresses DNA recombination-mediated VSG switching events. However, the mechanism of TbRAP1-mediated VSG silencing is still poorly understood. Like other RAP1 orthologs, TbRAP1 has conserved functional domains. We have identified that the Myb domain of TbRAP1 is required for its interaction with T. brucei TTAGGG repeat-binding factor (TbTRF), while the BRCT domain is required for its self-interaction. Furthermore, the TbRAP1 MybLike domain contains a bipartite nuclear localization signal (NLS) that is required for its interaction with importin-alpha and its nuclear localization. However, how is TbRAP1 localized to the telomere was unclear. Known RAP1 homologs either bind telomere DNA directly through their Myb and Myblike domains or are recruited to the telomere through their interaction with duplex telomere DNA binding factors. We have identified both a double-stranded and a single-stranded DNA binding activities in TbRAP1. Both these activities depend on a short, highly positively charged peptide that resides in the MybLike domain and overlaps with the TbRAP1 NLS. Surprisingly, we have also identified an RNA Recognition Motif (RRM)-mediated RNA binding activity in TbRAP1, a novel finding in RAP1 homologs. TbRAP1 RRM recognizes consensus sequences of VSG 3’UTRs in vitro and binds the active VSG RNA in vivo. Concentration-dependent competition between TbRAP1’s RNA and dsDNA binding activities suggests a novel mechanism where the active VSG RNA can antagonize the local TbRAP1 dsDNA binding-mediated VSG silencing to sustain VSG monoallelic expression. Recently we also have identified TbTRF-Interacting Factor 3 (TbTIF3) in a yeast 2-hybrid screen. We observed that TbTIF3 is essential for T. brucei proliferation and a transient depletion of TbTIF3 leads to a mild increase in the VSG switching frequency. Interestingly, TbTIF3-depleted cells have elongated telomere single-stranded 3’ overhangs, the long single-stranded 3’ overhang is prone to induce DNA recombination, which likely contributes to the increased VSG switching rate observed in TbTIF3-depleted.
Bibo Li, Ph.D. (Advisor)
Aaron Severson, Ph.D. (Committee Member)
Donny D. Licatalosi (Committee Member)
Zihua Gong, M.D., Ph.D. (Committee Member)
Valentin Börner, Ph.D. (Committee Member)
Merlin Nithya Gnanapragasam, Ph.D. (Committee Member)
230 p.
Biology; Genetics; Molecular Biology; Parasitology
Trypanosoma brucei, Antigenic Variation, VSG silencing, RRM, Monoallelic Expression, VSG switching

Recommended Citations

Citations

  • Afrin, M. (2022). Functions of Trypanosoma brucei RAP1 in Antigenic Variation [Doctoral dissertation, Cleveland State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=csu1655616654470721

    APA Style (7th edition)

  • Afrin, Marjia. Functions of Trypanosoma brucei RAP1 in Antigenic Variation. 2022. Cleveland State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=csu1655616654470721.

    MLA Style (8th edition)

  • Afrin, Marjia. "Functions of Trypanosoma brucei RAP1 in Antigenic Variation." Doctoral dissertation, Cleveland State University, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=csu1655616654470721

    Chicago Manual of Style (17th edition)

csu1655616654470721
25
© 2022, all rights reserved.
This open access ETD is published by Cleveland State University and OhioLINK.