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Sir Antagonist 1 (San1) Is a Ubiquitin Ligase* Received for publication, January 27, 2004, and in revised form, April 9, 2004
 

Summary: Sir Antagonist 1 (San1) Is a Ubiquitin Ligase*
Received for publication, January 27, 2004, and in revised form, April 9, 2004
Published, JBC Papers in Press, April 12, 2004, DOI 10.1074/jbc.M400894200
Arindam Dasgupta, Kerrington L. Ramsey, Jeffrey S. Smith, and David T. Auble
From the Department of Biochemistry and Molecular Genetics, University of Virginia Health System,
Charlottesville, Virginia 22908-0733
Mutations in Sir Antagonist 1 (SAN1) suppress defects
in SIR4 and SPT16 in Saccharomyces cerevisiae. San1
contains a RING domain, suggesting that it functions by
targeting mutant sir4 and spt16 proteins for degrada-
tion by a ubiquitin-mediated pathway. Consistent with
this idea, mutant sir4 and spt16 proteins are unstable in
SAN1 cells but are stabilized in san1 cells. We demon-
strate that San1 possesses ubiquitin-protein isopeptide
ligase activity in vitro, and the ubiquitin-protein isopep-
tide ligase activity of San1 is required for its function in
vivo. Wild-type Sir4 has a half-life of about 21 min, and
san1 increased Sir4 half-life to >90 min. In contrast,
san1 did not affect the stability of wild-type Spt16,
Sir3, Sir2, or the Spt16-associated proteins Pob3 and

  

Source: Auble, David - Department of Biochemistry and Molecular Genetics, University of Virginia

 

Collections: Biology and Medicine