TAME

TAME (Tosyl-L-Arginine Methyl Ester) is a small molecule APC (Anaphase-promoting complex/cyclosome) inhibitor with IC50 of 12 μM in Xenopus oocytes. [1]

APC is an ubiquitin ligase with multi subunits. It ubiquitinates substrates (e.g. cyclin B1 and secrin) and make them the targets for degradation with 26s proteasome, resulting in initiation of anaphase and mitotic exit. [2]

In mitotic Xenopus oocytes, TAME competes with the Cdc20 C-terminal IR-tail for APC binding to inhibit APC-dependent proteolysis. [3] TAME also stabilizes cyclin B1via terminating ubiquitination prenaturally. It slows the unmodified cyclin B1 initial ubiquitination. In the presence of TAME, ubiquitinated cyclin B1 is not able to promote Cdc20 binding to the APC. [4]

References:
1．Verma R, Oania R, Graumann J, Deshaies RJ.  Multiubiquitin chain receptors define a layer of substrate selectivity in the ubiquitin-proteasome system. Cell. 2004 Jul 9;118(1):99-110.
2．Peters JM.  The anaphase promoting complex/cyclosome: a machine designed to destroy. Nat Rev Mol Cell Biol. 2006; 7:644–656.
3．Zeng X, Sigoillot F, Gaur S, Choi S, Pfaff KL, Oh DC, Hathaway N, Dimova N, Cuny GD, King RW.  Pharmacologic inhibition of the anaphase-promoting complex induces a spindle checkpoint-dependent mitotic arrest in the absence of spindle damage. Cancer Cell. 2010 Oct 19;18(4):382-95.
4.  Zeng X, King RW. An APC/C inhibitor stabilizes cyclin B1 by prematurely terminating ubiquitination. Nat Chem Biol. 2012 Feb 26;8(4):383-92.