PROSITE documentation PDOC51469
SUN domain profile


Sad1/UNC-84 (SUN)-domain proteins are inner nuclear membrane (INM) proteins that are part of bridging complexes linking cytoskeletal elements with the nucleoskeleton. Originaly identified based on an ~150-amino acid region of homology between the C terminus of the Schizosaccharomyces pombe Sad1 protein and the Caenorhabditis elegans UNC-84 protein, SUN proteins are present in the proteomes of most eucaryotes. In addition to the SUN domain, these proteins contain a transmembrane sequence and at least one coiled-coil domain and localize to the inner nuclear envelope. SUN proteins are anchored in the inner nuclear envelope by their transmembrane segment and oriented in the membrane such that the C-terminal SUN domain is located in the space between the inner and outer nuclear membrane. Here, the SUN domain can interact with the C-terminal tail of an outer nuclear envelope protein that binds to the cytoskeleton, including the centrosome [1,2,3].

Some proteins known to contain a SUN domain are listed below:

  • Fission yeast spindle pole body-associated protein Sad1.
  • Yeast spindle pole body assembly component MPS3, essential for nuclear division and fusion.
  • Yeast uncharacterized protein SLP1.
  • Caenorhabditis nuclear migration and anchoring protein UNC-84.
  • Caenorhabditis SUN domain-containing protein 1 (sun-1), involved in centrosome attachment to the nucleus.
  • Mammalian sperm-associated antigen 4 protein (SPAG4), may assist the organization and assembly of outer dense fibers (ODFs), a specific structure of the sperm tail.
  • Mammalian sperm-associated antigen 4-like protein (SPAG4L).
  • Mammalian SUN1.
  • Mammalian SUN2.
  • Mammalian SUN3.

The profile we developed covers the entire SUN domain.

Last update:

November 2009 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

SUN, PS51469; SUN domain profile  (MATRIX)


1AuthorsMans B.J. Anantharaman V. Aravind L. Koonin E.V.
TitleComparative genomics, evolution and origins of the nuclear envelope and nuclear pore complex.
SourceCell Cycle 3:1612-1637(2004).
PubMed ID15611647

2AuthorsJaspersen S.L. Martin A.E. Glazko G. Giddings T.H. Jr. Morgan G. Mushegian A. Winey M.
TitleThe Sad1-UNC-84 homology domain in Mps3 interacts with Mps2 to connect the spindle pole body with the nuclear envelope.
SourceJ. Cell Biol. 174:665-675(2006).
PubMed ID16923827

3AuthorsGraumann K. Runions J. Evans D.E.
TitleCharacterization of SUN-domain proteins at the higher plant nuclear envelope.
SourcePlant J. 0:0-0(2009).
PubMed ID19807882

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