Eukaryotic
Eukaryotes have at least six SMC proteins in individual organisms, and they form three distinct heterodimers with specialized functions:
- A pair of SMC1 and SMC3 constitutes the core subunits of the cohesin complexes involved in sister chromatid cohesion.
- Likewise, a pair of SMC2 and SMC4 acts as the core of the condensin complexes implicated in chromosome condensation.
- A dimer composed of SMC5 and SMC6 functions as part of a yet-to-be-named octameric complex implicated in DNA repair and checkpoint responses.
Each complex contains a distinct set of non-SMC regulatory subunits.
Some organisms have variants of SMC proteins. For instance, mammals have a meiosis-specific variant of SMC1, known as SMC1β. The nematode Caenorhabditis elegans has an SMC4-variant that has a specialized role in dosage compensation.
| subfamily | complex | S. cerevisiae | S. pombe | C. elegans | D. melanogaster | vertebrates |
|---|---|---|---|---|---|---|
| SMC1α | cohesin | Smc1 | Psm1 | SMC-1 | DmSmc1 | SMC1α |
| SMC1β | cohesin (meiotic) | - | - | - | - | SMC1β |
| SMC2 | condensin | Smc2 | Cut14 | MIX-1 | DmSmc2 | CAP-E |
| SMC3 | cohesin | Smc3 | Psm3 | SMC-3 | DmSmc3 | SMC3 |
| SMC4 | condensin | Smc4 | Cut3 | SMC-4 | DmSmc4 | CAP-C |
| SMC4 variant | dosage compensation complex | - | - | DPY-27 | - | - |
| SMC5 | SMC5-6 | Smc5 | Smc5 | C27A2.1 | CG32438 | SMC5 |
| SMC6 | SMC5-6 | Smc6 | Smc6/Rad18 | C23H4.6, F54D5.14 | CG5524 | SMC6 |
Read more about this topic: SMC Protein, Species Distribution