Alternative titles; symbols
HGNC Approved Gene Symbol: SAE1
Cytogenetic location: 19q13.32 Genomic coordinates (GRCh38): 19:47,130,835-47,210,636 (from NCBI)
Posttranslational modification of proteins by the addition of the small protein SUMO (see SUMO1; 601912), or sumoylation, regulates protein structure and intracellular localization. SAE1 and UBA2 (613295) form a heterodimer that functions as a SUMO-activating enzyme for the sumoylation of proteins (Okuma et al., 1999).
By sequencing peptide fragments of the purified HeLa cell SUMO1-activating enzyme (SAE), followed by EST database analysis and RT-PCR, Desterro et al. (1999) cloned SAE1 and SAE2 (UBA2). The deduced SAE1 and SAE2 proteins contain 347 and 640 amino acids, respectively. SAE1 shares sequence similarity with the N terminus of ubiquitin-activating E1 enzymes (see UBE1; 314370), and SAE2 share sequence similarity with the C terminus of E1 enzymes. Both SAE subunits contain a conserved nucleotide-binding motif, and SAE2 contains an E1-like active-site cysteine. SAE1 has a calculated molecular mass of 38 kD. It had an apparent molecular mass of 40 kD by SDS-PAGE.
By searching an EST database for sequences similar to yeast Aos1 and Uba2, followed by screening a HeLa cell cDNA library, Okuma et al. (1999) cloned human SUA1 and UBA2, respectively.
Using Northern blot analysis, Azuma et al. (2001) detected expression of Sae1, which they called Aos1, in all adult mouse tissues examined, as well as in mouse embryos. Western blot analysis of synchronized HeLa cells detected increased AOS1 expression as cells progressed through S phase, followed by a substantial decrease in G2 phase. Immunofluorescence analysis showed AOS1 and UBA2 distributed throughout nuclei, but they were excluded from nucleoli. AOS1 and UBA2 copurified through a number of chromatography steps, suggesting they form a tight complex.
Desterro et al. (1999) showed that purified SAE from HeLa cells bound to immobilized SUMO1 in the presence of ATP. Use of in vitro transcribed and translated SAE1 and SAE2 showed that SUMO1 binding required both SAE subunits and involved a direct thioester linkage between the catalytic cysteine of SAE2 and SUMO1. Both SAE1 and SAE2 were required to transfer SUMO1 to the SUMO1-conjugating enzyme UBC9 (UBE2I; 601661). In the presence of SAE1, SAE2, UBC9, and ATP, SUMO1 was conjugated to recombinant I-kappa-B-alpha (NFKBIA; 164008). Desterro et al. (1999) concluded that the SAE1/SAE2 dimer functions in SUMO1 activation in a manner analogous to the single E1 ubiquitin-activating enzymes.
The sumoylated form of RANGAP1 (602362) associates with the nuclear pore complex and is required for import of proteins into the nucleus. Okuma et al. (1999) showed that SUA1, UBA2, and UBC9 catalyzed in vitro sumoylation of RANGAP1. Faint RANGAP1 modification was observed in the absence of UBC9. Okuma et al. (1999) concluded that, in contrast to the 3-step ubiquitination reaction, which requires an E1 ubiquitin-activating enzyme, an E2 ubiquitin-conjugating enzyme, and an E3 ubiquitin ligase, sumoylation is a 2-step reaction in which the SUA1/UBA2 dimer functions as an E1 enzyme and UBC9 functions as an E2 enzyme.
Gong et al. (1999) showed that AOS1 was required for sumoylation of UBA2 by epitope-tagged sentrin-1 (SUMO1), sentrin-2 (SUMO2; 603042), and sentrin-3 (SUMO3; 602231). UBA2 could bind ubiquitin (see 191339) and NEDD8 (603171) in the presence or absence of ATP, but no UBA2 conjugates were formed with these small protein modifiers in the presence of AOS1 and ATP.
By screening for short hairpin RNAs (shRNAs) that altered the fitness of mammary epithelial cells only in the presence of aberrant MYC (190080) signaling, Kessler et al. (2012) identified SAE1 and SAE2 (UBA2) as MYC-synthetic lethal genes. Inactivation of SAE2 led to mitotic catastrophe and cell death upon MYC hyperactivation. SAE2 inhibition switched a MYC transcriptional subprogram from activated to repressed. A subset of sumoylation-dependent MYC switchers (SMS genes), including CASC5 (609173), BARD1 (601593), and CDC20 (603618), was required for mitotic spindle function and to support the MYC oncogenic program. Sae2 was required for growth of Myc-dependent tumors in mice. Transduction of MYC-dependent breast cancer cells with inducible SAE2 shRNA suggested that SAE2 was required for growth and fitness of these cell lines. Gene expression analysis of human breast cancers with hyperactive MYC suggested that low expression of SAE1 and SAE2 resulted in better metastasis-free survival. Kessler et al. (2012) proposed that altering distinct subprograms of MYC transcription, such as by SAE2 inactivation, may be a therapeutic strategy in MYC-driven cancers.
E1 enzymes activate ubiquitin and ubiquitin-like proteins, such as SUMO, in 2 steps by C-terminal adenylation and thioester bond formation to a conserved catalytic cysteine in the E1. Olsen et al. (2010) reported the crystal structures of the SUMO E1, a dimer of SAE2 and UBA2, in complex with SUMO adenylate and tetrahedral intermediate analogs at 2.45- and 2.6-angstrom resolution, respectively. They found that the switch between the 2 half-reactions was accompanied by a 130-degree rotation of the cys domain of UBA2 and remodeling of key structural elements that displaced side chains required for adenylation with side chains required for thioester bond formation.
Hartz (2010) mapped the SAE1 gene to chromosome 19q13.32 based on an alignment of the SAE1 sequence (GenBank AF046025) with the genomic sequence (GRCh37).
Azuma, Y., Tan, S.-H., Cavenagh, M. M., Ainsztein, A. M., Saitoh, H., Dasso, M. Expression and regulation of the mammalian SUMO-1 E1 enzyme. FASEB J. 15: 1825-1827, 2001. Note: Full Article Published Online June 18, 2001. [PubMed: 11481243] [Full Text: https://doi.org/10.1096/fj.00-0818fje]
Desterro, J. M. P., Rodriguez, M. S., Kemp, G. D., Hay, R. T. Identification of the enzyme required for activation of the small ubiquitin-like protein SUMO-1. J. Biol. Chem. 274: 10618-10624, 1999. [PubMed: 10187858] [Full Text: https://doi.org/10.1074/jbc.274.15.10618]
Gong, L., Li, B., Millas, S., Yeh, E. T. H. Molecular cloning and characterization of human AOS1 and UBA2, components of the sentrin-activating enzyme complex. FEBS Lett. 448: 185-189, 1999. [PubMed: 10217437] [Full Text: https://doi.org/10.1016/s0014-5793(99)00367-1]
Hartz, P. A. Personal Communication. Baltimore, Md. 3/4/2010.
Kessler, J. D., Kahle, K. T., Sun, T., Meerbrey, K. L., Schlabach, M. R., Schmitt, E. M., Skinner, S. O., Xu, Q., Li, M. Z., Hartman, Z. C., Rao, M., Yu, P., and 15 others. A SUMOylation-dependent transcriptional subprogram is required for Myc-driven tumorigenesis. Science 335: 348-353, 2012. [PubMed: 22157079] [Full Text: https://doi.org/10.1126/science.1212728]
Okuma, T., Honda, R., Ichikawa, G., Tsumagari, N., Yasuda, H. In vitro SUMO-1 modification requires two enzymatic steps, E1 and E2. Biochem. Biophys. Res. Commun. 254: 693-698, 1999. [PubMed: 9920803] [Full Text: https://doi.org/10.1006/bbrc.1998.9995]
Olsen, S. K., Capili, A. D., Lu, X., Tan, D. S., Lima, C. D. Active site remodelling accompanies thioester bond formation in the SUMO E1. Nature 463: 906-912, 2010. [PubMed: 20164921] [Full Text: https://doi.org/10.1038/nature08765]