Structure of SA2 (blue) and RAD21 (green) (PDB 4PK7)

Cohesin subunit SA-1 (SA1) is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

that in humans is encoded by the ''STAG1''

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

. SA1 is a subunit of the

Cohesin Cohesin is a protein complex that mediates sister chromatid cohesion, homologous recombination, and DNA looping. Cohesin is formed of SMC3, SMC1, SCC1 and SCC3 ( SA1 or SA2 in humans). Cohesin holds sister chromatids together after DNA rep ...

complex which mediates sister chromatid cohesion,

homologous recombination Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...

and DNA looping. In somatic cells cohesin is formed of

SMC3 Structural maintenance of chromosomes protein 3 (SMC3) is a protein that in humans is encoded by the SMC3 gene. SMC3 is a subunit of the Cohesin complex which mediates sister chromatid cohesion, homologous recombination and DNA looping. Cohesin ...

, SMC1, RAD21 and either SA1 or SA2 whereas in

meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately resu ...

, cohesin is formed of SMC3,

SMC1B Structural maintenance of chromosomes protein 1B (SMC-1B) is a protein that in humans is encoded by the ''SMC1B'' gene. SMC-1B belongs to a family of proteins required for chromatid cohesion and DNA recombination during meiosis and mitosis. SMC1ß ...

REC8 Meiotic recombination protein REC8 homolog is a protein that in humans is encoded by the ''REC8'' gene. Rec8 is a meiosis-specific component of the cohesin complex that binds sister chromatids in preparation for the two divisions of meiosis. Rec8 ...

and SA3.

Structure and Interactions

SA1 is one of three human homologues of the yeast protein Scc3 which is a core subunit of the cohesin complex (the three human paralogues are SA1, SA2 and SA3). SA1 and SA2 are expressed in somatic cells whereas SA3 is the main SA paralogue in meiotic cells. SA1 stably binds to cohesin via the RAD21 subunit and functions as a platform for other regulatory subunits. SA1 has roles in regulating both cohesin loading and release.

References

External links

* * {{gene-3-stub