SUN (Sad1p, UNC-84) domains are conserved C-terminal protein regions a few hundred amino acids long. SUN domains are usually found following a transmembrane domain and a less conserved region of amino acids. Most proteins containing SUN domains are thought to be involved in the positioning of the nucleus in the cell. It is thought that SUN domains interact directly with KASH domains in the space between the outer and inner nuclear membranes to bridge the nuclear envelope and transfer force from the nucleoskeleton to the cytoplasmic cytoskeleton which enables mechanosensory roles in cells. SUN proteins are thought to localize to the inner nuclear membrane. The S. pombe Sad1 protein localises at the spindle pole body. In mammals, the SUN domain is present in two proteins, Sun1 and Sun2. The SUN domain of Sun2 has been demonstrated to be in the periplasm.
Examples of SUN Proteins
- SUN1, SUN2, SUN3, SUN4, SUN5
- SUN1, SUN2
- Uzer G, Thompson WR, Sen B, Xie Z, Yen SS, Miller S, Bas G, Styner M, Rubin CT, Judex S, Burridge K, Rubin J (June 2015). "Cell Mechanosensitivity to Extremely Low-Magnitude Signals Is Enabled by a LINCed Nucleus". Stem Cells. 33 (6): 2063–76. doi:10.1002/stem.2004. PMC 4458857. PMID 25787126.
- Tzur YB, Wilson KL, Gruenbaum Y (October 2006). "SUN-domain proteins: 'Velcro' that links the nucleoskeleton to the cytoskeleton". Nature Reviews. Molecular Cell Biology. 7 (10): 782–8. doi:10.1038/nrm2003. PMID 16926857.
- Hodzic DM, Yeater DB, Bengtsson L, Otto H, Stahl PD (June 2004). "Sun2 is a novel mammalian inner nuclear membrane protein". The Journal of Biological Chemistry. 279 (24): 25805–12. doi:10.1074/jbc.M313157200. PMID 15082709.
- Raff JW (September 1999). "The missing (L) UNC?". Current Biology. 9 (18): R708–10. doi:10.1016/S0960-9822(99)80446-1. PMID 10508607.