RNF1

RNF1 (PF3D7_0314700) is a putative RING-domain E3 ubiquitin ligase of Plasmodium falciparum whose characterized biology is confined to its expression, localization, and transcriptional regulation during sexual development. The protein is expressed predominantly in sexual (gametocyte) stages, peaking at stage II, and localizes to both the nucleus and cytoplasm (PMID:28791254). Its expression is under epigenetic control: histone hyperacetylation induced by the histone deacetylase inhibitor trichostatin A elevates both transcript and protein levels in mature gametocytes, and chromatin immunoprecipitation places acetylated histones at the Pfrnf1 promoter and coding regions, indicating that acetylation-associated chromatin positively regulates RNF1 expression (PMID:28791254). Beyond this expression and regulatory profile, no substrate, catalytic activity, interaction partner, or functional phenotype for RNF1 has been characterized in the available corpus.

1. 2017 Medium

   Establishing when and where RNF1 acts required defining its stage specificity and subcellular distribution, which was unknown; the finding placed RNF1 in sexual-stage parasites with dual nuclear/cytoplasmic localization.

   Evidence Immunochemistry/immunofluorescence localization across gametocyte stages in P. falciparum

   PMID:28791254

   Open questions at the time

   • No substrate or ubiquitin-ligase activity demonstrated for RNF1
   • No functional phenotype (e.g. knockout or knockdown effect on gametocytogenesis) established
   • Dual localization not resolved to specific compartments or interaction partners
2. 2017 Medium

   How RNF1 expression is controlled was unknown; showing that HDAC inhibition raises RNF1 levels and that acetylated histones occupy its locus established that RNF1 is positively regulated by histone acetylation.

   Evidence Microarray transcriptomics, immunochemistry, and ChIP of acetylated histones at the Pfrnf1 locus after trichostatin A treatment in P. falciparum

   PMID:28791254

   Open questions at the time

   • Specific histone marks and writer/eraser enzymes responsible not identified
   • Whether acetylation-driven induction alters RNF1 function or only abundance is unknown
   • Downstream consequences of RNF1 upregulation for gametocyte biology not tested

• The core biochemical role of RNF1 remains unresolved: no ubiquitin-ligase activity, substrate, interaction partner, or loss-of-function phenotype has been defined in the available corpus.
• No demonstration of E3 ubiquitin ligase catalytic activity
• No identified ubiquitination substrates or complex partners
• No genetic evidence for a role in gametocyte development or transmission