The SGOL1 gene is composed of 9 exons and spans 25698 bases.

Transcript variant A2 (NM_001012410) has the longest coding sequence and encodes a protein comprised of 561 aa. Transcript variant A1 (NM_001012409) lacks exon 9 and encodes a protein comprised of 527 aa. Typically, "SGOL1" corresponds to type A1 or A2. Transcript variant B2 (NM_001012412) lacks a large proportion of exon 6 and encodes a protein comprised of 309 aa. Transcript B1 (NM_001012411) lacks exon 9 in addition to a large proportion of exon 6 and encodes a protein comprised of 275 aa. Transcript C2 (NM_138484) skips exon 6 and encodes a protein comprised of 292 aa. Transcript C1 (NM_001012413) lacks exon 9 in addition to exon 6 and encodes a protein comprised of 258 aa. Transcript D1 (NM_001199257) lacks exon 7 and exon 8 in addition to a large proportion of exon 6 and encodes a protein comprised of 215 aa. Transcript P1 (AB567656) lacks exon 3, resulting in leading to a stop codon within exon 4, and encodes a protein comprised of 59 aa. Furthermore, several transcript variants that have an alternate 5 UTR exon are also stored in databases (NM_001199251, NM_001199253, NM_001199255, NM_001199252, NM_001199254 and NM_001199256).

There are two pseudogenes on chromosome 1 (PGOHUM00000244068) and chromosome 7 (PGOHUM00000232695).

SGOL1 protein (type A2) is a 64.2 kDa protein and has an N-terminal coiled-coil region, a P-V-I motif and a C-terminal conserved basic region. The N-terminal coiled-coil regions are required for the interaction with PP2A (Yamagishi et al., 2008) and the chromosomal passenger complex (CPC) (Tsukahara et al., 2010) at centromere. The P-V-I motif and the C-terminal basic region of SGOL1 are required for the interaction with HP1 (heterochromatin protein 1) and phosphorylated histone H2A at centromere, respectively (Yamagishi et al., 2008; Kawashima et al., 2010).

Serum antibodies against NY-BR-85, which encodes SGOL1, are detected in breast cancer patients, and the expression of NY-BR-85 mRNA was detected in several tissues, including thymus and testis (Scanlan et al., 2001). Expression of SGOL1 was also detected in the extraction of HeLa cells (Salic et al., 2004; Kitajima et al., 2005) and various human leukemia cell lines (Yang et al., 2013), while the expression of SGOL1 was downregulated in the colorectal cancers (Iwaizumi et al., 2009).

Nucleus. During prophase and metaphase, SGOL1 localizes to the inner centromere (Salic et al., 2004; Kitajima et al., 2005).

SGOL1 is a crucial factor to protect centromeric cohesin during mitosis and to maintain genomic stability in human cells. SGOL1-knockdown caused severe mitotic arrest and precocious separation of centromeric cohesion in HeLa cells (Salic et al., 2004; Kitajima et al., 2006) and HCT116 cells, resulting in chromosomal instability (Iwaizumi et al., 2009; Kahyo et al., 2011). In addition, SGOL1 was needed for the kinetochore localization of PLK1 and CENP-F in HeLa cells (Salic et al., 2004; Pouwels et al., 2007). Several short isoforms of SGOL1 showed aberrant cell phenotypes including unstable chromatid cohesion (Suzuki et al., 2006; Kahyo et al., 2011). These results suggest that the short isoforms of SGOL1 function as a negative factor to native SGOL1, and that abundant expression of the SGOL1 short isoforms can be responsible for chromosomal instability.

The coiled-coil and basic regions of shugoshin or shugoshin-like proteins are highly conserved between different species (Kitajima et al., 2004). SGOL2, a paralogue of SGOL1, was required for the PP2A-mediated protection of cohesin and the MCAK-mediated chromosome congression in HeLa cells (Tanno et al., 2010).

Losses of heterozygosity at several polymorphic markers in SGOL1 locus (c.416+39_42delGAAA, c.504A>T and c.1461C>T) were detected in 31.2 % of human colorectal cancers (Iwaizumi et al., 2009).