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. 2007 Aug 27;178(5):785–798. doi: 10.1083/jcb.200704108

Figure 1.

Figure 1.

The mammalian SUN protein family. Sun1 features four hydrophobic sequences, H1–H4, each of roughly 20 amino acid residues. Its membrane-spanning domain is contained within the H2–H4 region. The Sun1 N terminus, including H1, is nucleoplasmic. The C-terminal SUN domain resides in the PNS. Murine but not primate Sun1 contains a predicted C2H2 zinc finger. Several splice isoforms of mouse Sun1 have been identified that feature the loss of sequences encoded by exons 6–8, including H1. Corresponding GenBank/EMBL/DDBJ accession nos. are BAB29445 (Sun1Δ6–8), AAT90501 (Sun1Δ6), and BAC29339 (Sun1Δ8). Four other mammalian SUN proteins are known. Sun2 is ubiquitously expressed and localizes to the INM. Sun3 (SUNC1), Sun4 (SPAG4), and Sun5 (SPAG4L; GenBank/EMBL/DDBJ accession no. NP_542406) appear to be expressed primarily in testis (unpublished data). When expressed in HeLa cells, Sun3 localizes to the NE (Fig. S2, available at http://www.jcb.org/cgi/content/full/jcb.200704108/DC1), whereas Sun4 (Hasan et al., 2006) and Sun5 (unpublished data) localize primarily to the ER.