The SMC6 was discovered first in fission yeast as RAD18 (SMC6). It forms a heterodimeric complex with Spr18 (SMC5) protein.[7][8] In yeast, SMC5/6 complex has sub-units which consists of SMC5, SMC6 and six nonstructural maintenance of chromosomes (NSE) proteins. Nse1-Nse3-Nse4 subunits bridge the Smc5 head Smc6 and allow the binding of DNA.[9][10][11]
This depicts the placement of Nse proteins along the SMC5/6 complex in budding and fission yeast. This image does not include Nse2, as its position in the complex is not currently known.
Nse1-Nse3-Nse4 subunits bridge the heads of the Smc5 and Smc6 proteins and allow the complex to bind DNA. Nse5 and Nse6 form a sub-complex which localizes to the head of the SMC5/6 complex in the budding yeast Saccharomyces cerevisiae, and to the hinges of the SMC5/6 complex in the fission yeast Schizosaccharomyces pombe. The Nse5/6 sub-complex is required for the replication of S. cerevisiae, but has not been characterized as essential in S. pombe. Orthologous proteins to Nse5-Nse6 exist in other eukaryotes, namely ASAP1-SNI1 in Arabidopsis thaliana and SLF1-SLF2 in humans, which are believed have similar function to their Nse counterparts. The localization of SLF1 and SLF2 on the human SMC5/6 complex is unknown.[13][14]
The Smc5/6 complex has localization methods which are not heavily conserved. In humans the complex is localized to viral DNA sequences using SMC5/6 localization factors 1 and 2 (SLF1 and SLF2) which contributes to viral resistance.[15] In the plant A. thaliana, this heterodimer can be localized to double stranded breaks for homologous recombination using the SWI3B complex of the SWI/SNF pathway.[16] Once localized to the DNA, the SCM5/6 complex non-specifically binds to ~20 DNA base pairs.[17]
^Potts PR, Yu H (2007). "The SMC5/6 complex maintains telomere length in ALT cancer cells through SUMOylation of telomere-binding proteins". Nat. Struct. Mol. Biol. 14 (7): 581–90. doi:10.1038/nsmb1259. PMID17589526. S2CID7915836.
^Onoda F, Takeda M, Seki M, Maeda D, Tajima J, Ui A, Yagi H, Enomoto T (2004). "SMC6 is required for MMS-induced interchromosomal and sister chromatid recombinations in Saccharomyces cerevisiae". DNA Repair (Amst.). 3 (4): 429–39. doi:10.1016/j.dnarep.2003.12.007. PMID15010319.
^van der Crabben SN, Hennus MP, McGregor GA, Ritter DI, Nagamani SC, Wells OS, Harakalova M, Chinn IK, Alt A, Vondrova L, Hochstenbach R, van Montfrans JM, Terheggen-Lagro SW, van Lieshout S, van Roosmalen MJ, Renkens I, Duran K, Nijman IJ, Kloosterman WP, Hennekam E, Orange JS, van Hasselt PM, Wheeler DA, Palecek JJ, Lehmann AR, Oliver AW, Pearl LH, Plon SE, Murray JM, van Haaften G (2016). "Destabilized SMC5/6 complex leads to chromosome breakage syndrome with severe lung disease". J. Clin. Invest. 126 (8): 2881–92. doi:10.1172/JCI82890. PMC4966312. PMID27427983.
