The SAGA (Spt-Ada-Gcn5-Acetyltransferase) transcriptional co-activator is a protein complex that regulates inducible yeast genes by performing multiple functions including acetylating core histones, recruiting the RNA polymerase II preinitiation complex, and deubiquitinating histone H2B. The deubiquitinating activity of SAGA resides in a distinct sub-complex called the deubiquitinating module (DUBm), which consists of four proteins that are conserved across eukaryotes: Ubp8, Sgf11, Sus1 and Sgf73. The DUBm proteins are organized into two lobes around the globular domains of Ubp8 [1]. In SAGA, Sus1 binds to Sgf11 by wrapping around this N-terminal domain of Sgf11, forming a stable dimer [2-4].

1: A role for intersubunit interactions in maintaining SAGA deubiquitinating module structure and activity. Samara NL, Ringel AE, Wolberger C; Structure. 2012;20:1414-1424. PMID:22771212

2: Structural basis for the interaction between yeast Spt-Ada-Gcn5 acetyltransferase (SAGA) complex components Sgf11 and Sus1. Ellisdon AM, Jani D, Kohler A, Hurt E, Stewart M; J Biol Chem. 2010;285:3850-3856. PMID:20007317

3: Structural basis for assembly and activation of the heterotetrameric SAGA histone H2B deubiquitinase module. Kohler A, Zimmerman E, Schneider M, Hurt E, Zheng N; Cell. 2010;141:606-617. PMID:20434206

4: Structural insights into the assembly and function of the SAGA deubiquitinating module. Samara NL, Datta AB, Berndsen CE, Zhang X, Yao T, Cohen RE, Wolberger C; Science. 2010;328:1025-1029. PMID:20395473