DDX17

PF3D7_1445900 (DDX17) is an ATP-dependent RNA helicase of Plasmodium falciparum implicated in RNA metabolism during intraerythrocytic development (PMID:33981864). Biochemical reconstitution of the purified recombinant protein shows DNA- and RNA-stimulated ATPase activity but strictly RNA-directed unwinding, with ATP as the preferred cofactor, defining it as an RNA-specific helicase (PMID:33981864). The protein is most highly expressed at the trophozoite stage, where it localizes to the cytoplasm and the infected red blood cell membrane, and dsRNA-mediated knockdown impairs cell cycle progression, indicating a functional requirement for normal intraerythrocytic proliferation (PMID:33981864). Independently, DDX17 was captured by proximity labelling near the male-fate determinant Md1 within cytoplasmic RNP granule-like structures during gametocytogenesis, placing it adjacent to the translational-repression machinery (PMID:36477538). Beyond these observations, the direct RNA substrates, molecular partners, and the mechanism linking its helicase activity to cell cycle progression have not been characterized in the available corpus.

1. 2021 Medium

   Establishing whether PF3D7_1445900 is a genuine helicase and on which nucleic-acid substrate it acts was needed to assign a molecular activity; in vitro reconstitution showed it is an ATP-dependent, RNA-specific unwinding enzyme.

   Evidence ATPase and time-dependent helicase assays with purified recombinant protein on RNA and DNA substrates

   PMID:33981864

   Open questions at the time

   • No physiological RNA substrate identified
   • No structural model of the helicase core
   • In vitro activity not linked to a cellular process
2. 2021 Low

   Defining when and where the enzyme acts during the blood stage was needed to place its activity in a developmental context; expression and localization data pointed to a trophozoite-stage cytoplasmic and iRBC-membrane role.

   Evidence qRT-PCR across intraerythrocytic stages and immunofluorescence microscopy of trophozoites

   PMID:33981864

   Open questions at the time

   • Single method for each readout with no orthogonal confirmation
   • Functional consequence of iRBC-membrane localization unknown
   • No quantitative or dynamic localization across the full cycle
3. 2021 Low

   Whether the helicase is functionally required in the parasite was addressed by depletion; dsRNA knockdown impaired cell cycle progression, establishing a physiological role in intraerythrocytic proliferation.

   Evidence dsRNA-mediated knockdown with cell cycle progression phenotype readout

   PMID:33981864

   Open questions at the time

   • No molecular epistasis or pathway placement
   • Downstream RNA targets mediating the phenotype unknown
   • Knockdown specificity and degree not molecularly validated
4. 2022 Low

   Whether PF3D7_1445900 participates in sexual-stage RNA regulation was addressed by mapping the neighborhood of the male-fate determinant Md1; proximity labelling placed DDX17 near cytoplasmic RNP granules associated with translational repression.

   Evidence TurboID proximity labelling with mass spectrometry (Md1-TurboID vs untagged WT) in gametocytes

   PMID:36477538

   Open questions at the time

   • Proximity labelling does not establish direct interaction
   • No functional characterization of DDX17 in gametocytes
   • Reciprocal validation and role within the RNP granule not shown

• The direct RNA substrates of DDX17, its molecular partners, and the mechanistic link between its unwinding activity and both cell cycle progression and RNP-granule-associated translational repression remain undefined.
• No physiological RNA targets identified
• No validated direct protein partners
• Mechanism connecting helicase activity to cell cycle and gametocyte RNP granules unresolved