CAPH

CAPH (PF3D7_1304000) is the kleisin subunit of the condensin I complex in Plasmodium falciparum and functions in nuclear division during intraerythrocytic schizogony (PMID:38564676). It physically associates with PfCAP-G, and inducible knockout of CAPH does not alter PfCAP-G expression but abolishes its localization to mitotic chromosomes, establishing CAPH as essential for loading and retention of the condensin I complex on chromosomes (PMID:38564676). Consistent with a mitotic role, CAPH is dynamically expressed across the erythrocytic cell cycle with peak expression at the metaphase plate (PMID:38564676). Loss of CAPH specifically abolishes karyokinesis — duplicated centrosomes remain clustered over an unsegmented nuclear mass — while mitotic spindle assembly and cytokinesis proceed normally, defining a dedicated requirement for nuclear division rather than spindle formation or cell division (PMID:38564676). Beyond its role in condensin I assembly and karyokinesis, no further mechanistic detail for CAPH has been characterized in the available corpus.

1. 2024 High

   Whether P. falciparum encodes a functional condensin I kleisin that organizes the complex on chromosomes was unresolved; this established CAPH as the kleisin required to load and retain condensin I on mitotic chromosomes.

   Evidence Inducible knockout with immunofluorescence showing loss of PfCAP-G chromosomal localization, plus co-immunoprecipitation confirming interaction with PfCAP-G

   PMID:38564676

   Open questions at the time

   • Direct interactions with other condensin I subunits beyond PfCAP-G not mapped
   • No structural or biochemical reconstitution of the CAPH-containing complex
   • Mechanism by which CAPH mediates chromosomal loading not defined
2. 2024 Medium

   The temporal deployment of CAPH during the cell cycle was unknown; live-imaging showed peak expression at the metaphase plate, linking CAPH function to the mitotic window.

   Evidence Immunofluorescence microscopy across erythrocytic cell cycle stages

   PMID:38564676

   Open questions at the time

   • Single-lab observation without independent replication
   • Regulation driving cell-cycle-dependent expression not identified
3. 2024 High

   Which step of division depends on CAPH was undefined; knockout revealed a specific failure of karyokinesis with intact spindle assembly and cytokinesis, pinpointing a dedicated nuclear-division role.

   Evidence Inducible knockout with orthogonal fluorescence markers for centrosome, spindle, and nucleus

   PMID:38564676

   Open questions at the time

   • Molecular basis linking condensin loading to nuclear segmentation not resolved
   • Fate of chromosomes within the unsegmented nuclear mass not characterized

• It remains unknown how CAPH-dependent condensin I loading is molecularly coupled to chromosome condensation and nuclear segmentation, and what other partners or regulators act at this step.
• No biochemical or structural definition of the full condensin I complex containing CAPH
• No identification of upstream regulators of CAPH loading
• Consequences for chromatin architecture during schizogony not measured