sun-1 (C. elegans) review notes

Session 1 (2026-09-27, claude-code)

Context: meiotic/embryonic SUN protein partnering the KASH protein ZYG-12; reviewed for
modules/linc_complex.yaml (SUN component; meiotic variant) alongside human SUN1/KASH5.

Identity

• Q20924, F57B1.2, also matefin/MTF-1. UniProt PANTHER PTHR12911:SF2 ("SUN DOMAIN-CONTAINING
  PROTEIN 1"), i.e. the SUN1-like subfamily, distinct from UNC-84 (PTHR12911:SF8, Koi-like).
• Type II INM protein PMID:19759181.

Function (with provenance)

• Binds ZYG-12 mini-KASH through a luminal region outside the SUN domain
  PMID:19759181.
• Embryonic centrosome-nucleus attachment PMID:14697201.
• Meiotic pairing: PMID:17543861;
  PMID:19913287 (fetched this session, PubMed-verified);
  PMID:19913286 (fetched, abstract only).
• Embryonic telomere anchoring with POT-1 PMID:24297748.
• CED-4 NE receptor in apoptosis PMID:16938876 (single study).
• Centrosome duplication suppressor PMID:17446307.

Decisions

• protein binding: ZYG-12 -> GO:0140444; CED-4 -> GO:0043495.
• intracellular protein localization -> MODIFY GO:0090435.
• GO:0034993 IBA ACCEPTED (contrast with UNC-84, where it was moved to GO:0106094).
• NEW: GO:0007129 homologous chromosome pairing at meiosis; GO:0005637 INM; GO:0034398 telomere tethering at nuclear periphery.
• Embryo development, regulation of centrosome duplication -> KEEP_AS_NON_CORE.

Module implications

• The worm splits SUN functions between paralogs: UNC-84 (somatic nuclear migration/anchorage) and
  SUN-1 (meiotic chromosome movement, embryonic centrosome attachment). In human, SUN1 does both
  meiotic and somatic work. The SUN-1/ZYG-12 pair is the worm counterpart of SUN1/KASH5, and
  supports a C. elegans meiotic variant in linc_complex.
• C. elegans attaches pairing centers, not telomeres, in meiosis, so GO:0070197 (used for human
  SUN1) does not fit exactly; GO:0007129 was used instead.
• SUN-1 binds ZYG-12 outside its SUN domain, an exception to the canonical SUN-domain-KASH groove
  model in the module.

Deep research

• sun-1-deep-research-falcon.md read; consistent. It adds lamin binding in vitro (Zuela 2016),
  MJL-1 at pairing centers (Kim 2023) and oocyte nuclear collapse after lamin loss (Liu 2023); not
  cached and not annotated.