RESUMEN
Synthetic routes for the preparation of O-acetyl-ADP-ribose and two novel non-hydrolyzable analogs containing an N-acetyl are described and shown to interact with the macro domain of histone protein H2A1.1.
Asunto(s)
Adenosina Difosfato Ribosa/biosíntesis , O-Acetil-ADP-Ribosa/biosíntesis , Acetilación , Modelos Moleculares , O-Acetil-ADP-Ribosa/química , Sirtuinas/metabolismoRESUMEN
The silent information regulator 2 (Sir2) family of NAD-dependent N-acetyl-protein deacetylases participates in the regulation of gene silencing, chromatin structure, and longevity. In the Sir2-catalyzed reaction, the acetyl moiety of N-acetyl-histone is transferred to the ADP-ribose of NAD, yielding O-acetyl-ADP-ribose and nicotinamide. We hypothesized that, if O-acetyl-ADP-ribose were an important signaling molecule, a specific hydrolase would cleave the (O-acetyl)-(ADP-ribose) linkage. We report here that the poly(ADP-ribose) glycohydrolase ARH3 hydrolyzed O-acetyl-ADP-ribose to produce ADP-ribose in a time- and Mg(2+)-dependent reaction and thus could participate in two signaling pathways. This O-acetyl-ADP-ribose hydrolase belongs to a family of three structurally related 39-kDa ADP-ribose-binding proteins (ARH1-ARH3). ARH1 was reported to hydrolyze ADP-ribosylarginine, whereas ARH3 degraded poly(ADP-ribose). ARH3-catalyzed generation of ADP-ribose from O-acetyl-ADP-ribose was significantly faster than from poly(ADP-ribose). Like the degradation of poly(ADP-ribose) by ARH3, hydrolysis of O-acetyl-ADP-ribose was abolished by replacement of the vicinal aspartates at positions 77 and 78 of ARH3 with asparagine. The rate of O-acetyl-ADP-ribose hydrolysis by recombinant ARH3 was 250-fold that observed with ARH1; ARH2 and poly(ADP-ribose) glycohydrolase were inactive. All data support the conclusion that the Sir2 reaction product O-acetyl-ADP-ribose is degraded by ARH3.
Asunto(s)
Glicósido Hidrolasas/metabolismo , O-Acetil-ADP-Ribosa/biosíntesis , Sirtuinas/metabolismo , Sustitución de Aminoácidos , Glicósido Hidrolasas/química , Glicósido Hidrolasas/genética , Humanos , Hidrólisis , Técnicas In Vitro , Cinética , Magnesio/metabolismo , Peso Molecular , Mutagénesis Sitio-Dirigida , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Sirtuina 1 , Espectrometría de Masa por Láser de Matriz Asistida de Ionización DesorciónRESUMEN
Assembly of silent chromatin domains in budding yeast involves the deacetylation of histone tails by Sir2 and the association of the Sir3 and Sir4 proteins with hypoacetylated histone tails. Sir2 couples deacetylation to NAD hydrolysis and the synthesis of a metabolite, O-acetyl-ADP-ribose (AAR), but the functional significance of NAD hydrolysis or AAR, if any, is unknown. Here we examine the association of the Sir2, Sir3, and Sir4 proteins with each other and histone tails. Our analysis reveals that deacetylation of histone H4-lysine 16 (K16), which is critical for silencing in vivo, is also critical for the binding of Sir3 and Sir4 to histone H4 peptides in vitro. Moreover, AAR itself promotes the association of multiple copies of Sir3 with Sir2/Sir4 and induces a dramatic structural rearrangement in the SIR complex. These results suggest that Sir2 activity modulates the assembly of the SIR complex through both histone deacetylation and AAR synthesis.
Asunto(s)
Histona Desacetilasas/metabolismo , Histonas/metabolismo , NAD/metabolismo , O-Acetil-ADP-Ribosa/metabolismo , Proteínas Reguladoras de Información Silente de Saccharomyces cerevisiae/metabolismo , Sitios de Unión/fisiología , Histona Desacetilasas/genética , Lisina/metabolismo , Sustancias Macromoleculares/metabolismo , O-Acetil-ADP-Ribosa/biosíntesis , Fosfoglicerato-Deshidrogenasa , Unión Proteica/fisiología , Estructura Terciaria de Proteína/fisiología , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas Reguladoras de Información Silente de Saccharomyces cerevisiae/genética , Sirtuina 2 , Sirtuinas/genética , Sirtuinas/metabolismoRESUMEN
The Sir2 family of enzymes is a recently described class of NAD(+)-dependent protein deacetylases that use NAD+ as a reactant to deacetylate acetyllysine residues of protein substrates to form the aminolysine sidechain and a novel product 2'-O-acetyl-ADP-ribose. The founding member of the Sir2 proteins, the yeast Sir2p, has been identified as a key member of SIR complexes responsible for the long-term silencing of genes in the yeast Saccharomyces cerevisiae. Increase of Sir2 activity by caloric restriction or osmotic stress increases genome stability and lifespan in this organism. The Sir2 reaction mechanism couples ADP-ribosyltransfer and hydrolysis reactions via the formation of a stabilized ADPR-peptidyl intermediate. Principles of the chemistry of stabilized ADPR intermediates are examined for Sir2 and the mechanistically related ADP-ribosylcyclase CD38. An examination of the crystal structures of Sir2 family members is presented with a view to the chemical requirements of the Sir2 reaction. The present review describes the current knowledge of the Sir2 reaction, the reaction mechanism and the regulation of Sir2.