Spatial dynamics of SIRT1 and the subnuclear distribution of NADH species

Significance Environmental and nutritional cues are crucial to determine genomic responses. They generally proceed through modulation of epigenetic mechanisms. Nuclear sirtuin 1 (SIRT1) is a well-known epigenetic modifier, because it deacetylates histones, and nutrient sensor, because its enzymatic activity is coupled to hydrolysis of NAD + . Compartmentalization of NAD + metabolism makes it difficult to predict the pace of NAD + -dependent reactions in cells. Here, we use nonlinear optics in live cells to define subnuclear distribution of free and bound NADH, which determines local enzymatic activity. We define subnuclear dynamics of SIRT1 and establish a biophysical signature for SIRT1 activity in live cells. These findings have far-reaching implications, because they describe unique aspects of SIRT1 activity and delineate subnuclear territories of metabolic cues.