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Understanding the role of RBR-E3 ligase in regulation of cellular homeostasis in human malaria parasite
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  • Niti Kumar,
  • Varsha Kumari,
  • Aradhya Tripathi,
  • Seema Vidyarthi,
  • Nirupa Chaurasia,
  • Shagufa Nisrat Noorie,
  • Simmi Anjum,
  • Mohammad Anas,
  • Shakil Ahmed
Niti Kumar
CSIR-Central Drug Research Institute

Corresponding Author:[email protected]

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Varsha Kumari
CSIR-Central Drug Research Institute
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Aradhya Tripathi
CSIR-Central Drug Research Institute
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Seema Vidyarthi
CSIR-Central Drug Research Institute
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Nirupa Chaurasia
CSIR-Central Drug Research Institute
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Shagufa Nisrat Noorie
CSIR-Central Drug Research Institute
Simmi Anjum
CSIR-Central Drug Research Institute
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Mohammad Anas
CSIR-Central Drug Research Institute
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Shakil Ahmed
CSIR-Central Drug Research Institute
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Abstract

E3 ligases constitute an important component of proteostasis machinery which plays critical role in malaria parasite survival through post-translational modifications of its protein-substrates. In contrast to humans, parasite E3 ligases have not been extensively studied. Here, we characterize a unique plasmodial E3 ligase that has both RING and HECT-like features with zinc-coordinating domains. Plasmodium encodes a single RING-between-RING (RBR) E3 ligase that has evolutionarily diverged from human and other intracellular parasites. Ubiquitination experiments showed that Pf RBR-E3 ligase catalyzes K6, K11, K48 and K63 mediated ubiquitination hinting towards its diverse biological roles (DNA repair, proteasomal degradation, mitophagy). Y2H experiments showed that this E3 ligase interacts with UBCH5 and UBC13 family of plasmodial E2-conjugating enzymes. Through mutational analysis, we identified residues in RING1 and RING2 domains critical for ubiquitination activity and protein stability of Pf RBR-E3 ligase. Experiments showed that Pf RBR-E3 ligase participates in maintenance of organellar homeostasis and exhibits differences in localization upon exposure to different genotoxic (MMS) and proteotoxic (MG132, FCCP and artemisinin derivative) stress. Our study open avenues for the exploration of parasite E3 ligases for design of protein degradation based intervention strategies which could minimize the risk of drug resistance.