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. Author manuscript; available in PMC: 2018 Dec 1.
Published in final edited form as: Cancer Metastasis Rev. 2017 Dec;36(4):717–736. doi: 10.1007/s10555-017-9705-x

Fig. 1.

Fig. 1

The ubiquitin-proteasome system (UPS). The pathway begins with the conjugation of ubiquitin molecules to a substrate protein, forming a polyubiquitin chain through E1, E2 and E3 enzymes. The chain is then recognized and removed by the 19S lid of the 26S proteasome, followed by either release or degradation of the protein by the 20S catalytic core.