NOP5

NOP5 (PF3D7_1008800) is a putative nucleolar protein of Plasmodium falciparum whose function has not been directly characterized in the available corpus. It was detected in the parasite nuclear proteome by high-accuracy mass spectrometry and is noted as one of only three proteins previously localized to the parasite nucleolus (PMID:23181666). In DNA oligonucleotide pull-downs using probes bearing the de novo regulatory motif 028, NOP5 co-enriched with the transcription factor AP2-I and chromatin-associated factors (bromodomain proteins, HMGB3, and a SWIB/MDM2 domain protein), placing it in physical association with a regulatory DNA motif complex during intraerythrocytic stages (PMID:29649445). Beyond this nucleolar localization and pull-down association, no enzymatic activity, structure, direct binding partner, or functional mechanism has been established for NOP5 itself in the available corpus.

1. 2012 Low

   Establishing where NOP5 resides, mass spectrometry of isolated nuclei placed it in the P. falciparum nuclear proteome and flagged its prior nucleolar localization, giving a first subcellular anchor for an otherwise uncharacterized protein.

   Evidence Organellar proteomics by high-accuracy mass spectrometry of isolated parasite nuclei

   PMID:23181666

   Open questions at the time

   • Detection in a pan-nuclear catalog only; no functional experiment performed on NOP5 itself
   • No enzymatic activity or molecular role assigned
   • Nucleolar assignment cited from prior work rather than demonstrated in this study
2. 2018 Low

   Asking what NOP5 associates with, DNA pull-downs showed it co-enriches with AP2-I and chromatin factors on a specific regulatory motif, providing the first (associative) link between this nucleolar protein and a transcriptional regulatory complex.

   Evidence DNA oligonucleotide pull-down with regulatory motif 028 probe followed by mass spectrometry, intraerythrocytic stages

   PMID:29649445

   Open questions at the time

   • Single large-scale pull-down without functional follow-up specific to NOP5
   • Association may be indirect; no reciprocal or direct binding validation for NOP5
   • No demonstration that NOP5 contributes to regulatory activity of the motif complex

• The direct molecular activity of NOP5, its role in nucleolar biology, and whether its association with the AP2-I regulatory motif complex is functional or incidental remain unknown.
• No enzymatic activity or biochemical function established
• No structure or direct binding partner defined
• No genetic perturbation or phenotype characterized