NCAPG2

NCAPG2 is a non-SMC subunit of the condensin II complex that ensures proper chromosome condensation and segregation during mitosis (PMID:25109385, PMID:30609410). Its highly conserved C-terminal region, when phosphorylated (residues 1007VLS-pT-L1011), directly binds the polo-box domain of PLK1 and recruits PLK1 to prometaphase kinetochores, promoting phosphorylation of the kinetochore substrate BubR1; loss of NCAPG2 loosens and misaligns spindle-kinetochore attachments in both human cells and C. elegans (PMID:25109385). Recessive loss-of-function mutations in NCAPG2 cause abnormal chromosome condensation, anaphase chromatin bridges, and micronuclei, and produce a human and zebrafish phenotype of microcephaly and renal anomalies that is rescued by wild-type but not mutant NCAPG2, establishing NCAPG2 as a causative disease gene (PMID:30609410). Beyond its mitotic role, NCAPG2 functions in transcriptional and signaling contexts: in hematopoietic cells it is recruited to the nucleus by the bHLH factors SCL and E12 and represses SCL/E12-mediated transcription to promote erythroid differentiation (PMID:16673016), and in cancer cells it directly binds STAT3 and drives STAT3 occupancy of the MYC promoter to activate c-MYC (PMID:38166947), activates HBO1 phosphorylation and Wnt/β-catenin signaling (PMID:32897418), and engages STAT3/NF-κB signaling (PMID:31176678). NCAPG2 expression is set post-transcriptionally, being stabilized by PCBP2 binding to its mRNA (PMID:37544634) and suppressed through 3'UTR-targeting regulators (PMID:41894088).

1. 2006 Medium

   The first mechanistic role for the NCAPG2 ortholog placed it outside mitosis, asking whether a condensin subunit could modulate hematopoietic transcription.

   Evidence Yeast two-hybrid, reciprocal Co-IP, luciferase reporter and MEL cell differentiation assays with the murine ortholog MTB/mCAP-G2

   PMID:16673016

   Open questions at the time

   • Mechanism by which nuclear recruitment by SCL/E12 represses transcription not defined
   • Mouse ortholog; human relevance not directly tested
   • No link to the condensin function established here
2. 2012 Medium

   Established that NCAPG2 is a druggable mitotic target by showing a small molecule can bind it and disrupt chromosome segregation.

   Evidence mRNA display in vitro binding selection of Q15 to hCAP-G2 plus immunofluorescence and xenograft readouts

   PMID:23028663

   Open questions at the time

   • Binding site on NCAPG2 not mapped
   • Direct mechanistic link between compound binding and segregation defect not resolved
3. 2014 High

   Resolved how NCAPG2 contributes mechanistically to mitosis, defining a direct phosphorylation-dependent interaction that recruits PLK1 to kinetochores.

   Evidence Co-IP, crystal structure of the PBD–NCAPG2 C-terminal phosphopeptide complex, phosphopeptide mutagenesis, kinase substrate assay, and siRNA/RNAi in human cells and C. elegans

   PMID:25109385

   Open questions at the time

   • Kinase responsible for the priming phosphorylation of NCAPG2 not identified
   • Whether condensin assembly is required for PLK1 recruitment not tested
4. 2019 Medium

   Connected NCAPG2 to oncogenic signaling, asking how its overexpression drives tumor phenotypes.

   Evidence Co-IP, luciferase reporter, ELISA and in vitro/in vivo functional assays in hepatocellular carcinoma linking NCAPG2 to STAT3/NF-κB and miR-188-3p

   PMID:31176678

   Open questions at the time

   • Direct versus indirect activation of STAT3/NF-κB not distinguished
   • Single tumor type
5. 2019 High

   Established NCAPG2 as a human disease gene by demonstrating causality of recessive loss-of-function alleles for chromosome instability and a microcephaly/renal phenotype.

   Evidence Patient fibroblast cytogenetics, zebrafish morpholino and CRISPR-F0 mutagenesis, mRNA rescue, and nphp1 epistasis

   PMID:30609410

   Open questions at the time

   • Tissue-specific basis of microcephaly versus renal phenotype not resolved
   • Relationship of condensation defect to the PLK1 recruitment role not directly connected
6. 2020 Medium

   Extended NCAPG2's signaling repertoire by placing it upstream of HBO1 acetyltransferase activation and Wnt/β-catenin signaling in glioblastoma.

   Evidence Knockdown/overexpression functional assays, phospho-HBO1 and H4 acetylation western blots, MCM chromatin-binding assay, HBO1 knockdown rescue

   PMID:32897418

   Open questions at the time

   • How NCAPG2 promotes HBO1 phosphorylation mechanistically unknown
   • Direct binding to HBO1 not shown
7. 2022 Medium

   Identified an upstream transcriptional regulator, showing brachyury directly drives NCAPG2 expression in HCC.

   Evidence ChIP-sequencing for brachyury occupancy plus knockdown functional assays and NCAPG2-brachyury epistasis in vitro and in vivo

   PMID:36119840

   Open questions at the time

   • Direct binding of brachyury to the NCAPG2 promoter not validated beyond ChIP-seq
   • Single tumor type
8. 2023 Medium

   Defined post-transcriptional control of NCAPG2 abundance by identifying PCBP2 as an mRNA-stabilizing factor.

   Evidence Direct RNA binding assay and mRNA half-life measurement (8 h to 5 h) upon PCBP2 knockdown in MCF-7 and T-47D cells

   PMID:37544634

   Open questions at the time

   • Binding element on NCAPG2 mRNA not mapped
   • Single lab
9. 2024 Medium

   Provided a direct transcriptional mechanism for NCAPG2 oncogenic activity by showing it binds STAT3 and induces STAT3 occupancy of the MYC promoter.

   Evidence Co-IP, ChIP, TMT proteomics and knockdown/overexpression with xenografts in prostate cancer

   PMID:38166947

   Open questions at the time

   • Whether NCAPG2 acts as a coactivator or alters STAT3 phosphorylation not resolved
   • Single lab
10. 2025 Low

    Added regulators acting through the NCAPG2 3'UTR, defining a USP52–RBM5–NCAPG2 suppressive axis and RPL35A as a positive upstream factor.

    Evidence Co-IP ubiquitination and dual-luciferase 3'UTR reporter assays (RBM5/USP52) and shRNA/overexpression with gene expression analysis (RPL35A), in prostate cancer and HCC

    PMID:40552444 PMID:41894088

    Open questions at the time

    • RPL35A regulation of NCAPG2 shown only by expression analysis without direct binding
    • Mechanism of RBM5 3'UTR-mediated suppression not detailed

• How NCAPG2's mitotic condensin function mechanistically relates to its diverse transcriptional and signaling roles remains unresolved.
• No unified model linking kinetochore PLK1 recruitment to STAT3/HBO1/SCL transcriptional functions
• The priming kinase for NCAPG2 phosphorylation is unidentified
• Whether signaling roles require the condensin complex is untested