The KASH (for Klarsicht/ANC-1/Syne-1 homology) or KLS domain is a highly hydrophobic nuclear envelope localisation domain of approximately 60 amino acids comprising a 20-amino-acid transmembrane region and a 30-35-residue C-terminal region that lies between the inner and the outer nuclear membranes [1]. During meiotic prophase, telomeres cluster to form a bouquet arrangement of chromosomes. SUN and KASH domain proteins form complexes that span both membranes of the nuclear envelope. The KASH domain links the dynein motor complex of the microtubules, through the outer nuclear membrane to the Sad1 domain in the inner nuclear membrane which then interacts with the bouquet proteins Bqt1 and Bqt2 that are complexed with Bqt4, Rap1 and Taz1 and attached to the telomere [2]. SUN domain-containing proteins are essential for recruiting KASH domain proteins at the outer nuclear membrane, and KASH domains provide a generic NE tethering device for functionally distinct proteins whose cytoplasmic domains mediate nuclear positioning, maintain physical connections with other cellular organelles, and possibly even influence chromosome dynamics [3].

1: Role of ANC-1 in tethering nuclei to the actin cytoskeleton. Starr DA, Han M; Science. 2002;298:406-409. PMID:12169658

2: Membrane proteins Bqt3 and -4 anchor telomeres to the nuclear envelope to ensure chromosomal bouquet formation. Chikashige Y, Yamane M, Okamasa K, Tsutsumi C, Kojidani T, Sato M, Haraguchi T, Hiraoka Y; J Cell Biol. 2009;187:413-427. PMID:19948484

3: Bringing KASH under the SUN: the many faces of nucleo-cytoskeletal connections. Razafsky D, Hodzic D; J Cell Biol. 2009;186:461-472. PMID:19687252