RESUMO
Cohesin complex mediates cohesion between sister chromatids, which promotes high-fidelity chromosome segregation. Eco1p acetylates the cohesin subunit Smc3p during S phase to establish cohesion. The current model posits that this Eco1p-mediated acetylation promotes establishment by abrogating the ability of Wpl1p to destabilize cohesin binding to chromosomes. Here we present data from budding yeast that is incompatible with this Wpl1p-centric model. Two independent in vivo assays show that a wpl1∆ fails to suppress cohesion defects of eco1∆ cells. Moreover, a wpl1∆ also fails to suppress cohesion defects engendered by blocking just the essential Eco1p acetylation sites on Smc3p (K112, K113). Thus removing WPL1 inhibition is insufficient for generating cohesion without ECO1 activity. To elucidate how ECO1 promotes cohesion, we conducted a genetic screen and identified a cohesion activator mutation in the SMC3 head domain (D1189H). Smc3-D1189H partially restores cohesion in eco1∆ wpl1∆ or eco1 mutant cells but robustly restores cohesion in cells blocked for Smc3p K112 K113 acetylation. These data support two important conclusions. First, acetylation of the K112 K113 region by Eco1p promotes cohesion establishment by altering Smc3p head function independent of its ability to antagonize Wpl1p. Second, Eco1p targets other than Smc3p K112 K113 are necessary for efficient establishment.
Assuntos
Acetiltransferases/metabolismo , Proteínas de Ciclo Celular/genética , Cromátides/genética , Proteínas Cromossômicas não Histona/genética , Segregação de Cromossomos , Proteínas Nucleares/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Acetilação , Acetiltransferases/genética , Sequência de Aminoácidos , Cromossomos Fúngicos , Dados de Sequência Molecular , Mutação , Proteínas Nucleares/genética , Fase S , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , CoesinasRESUMO
OBJECTIVES: To evaluate nicotine delivery from the NJOY® King Bold Electronic Nicotine Delivery System (ENDS) and its short-term potential for smoking reduction or cessation. METHODS: One week of ad libitum use was followed by measurements of plasma nicotine, heart rate, and craving and withdrawal after 12 hours of nicotine abstinence in 25 adult smokers not interested in quitting. RESULTS: After 5 minutes of use, blood nicotine levels increased by a mean of 3.5 ng/mL (p < .001), heart rate increased, and craving was reduced by 55%. Cigarettes per day were reduced by 39% during the test week, and perceptions of use for reduction or cessation were positive. CONCLUSIONS: The NJOY® King Bold ENDS delivers nicotine and led to short-term smoking reduction.