Sirtuin 1, はNAD-dependent deacetylase sirtuin-1, と呼ばれている蛋白でヒトでは SIRT1 遺伝子にコードされています。

SIRT1 はsirtuin (silent mating type information regulation 2 homolog) 1 (S. cerevisiae),を表し  yeast (Saccharomyces cerevisiae) の Sir2相同性のある蛋白で. 主に cell nucleus においてtranscription factors の脱アセチル化反応を行っています。それによって他の遺伝子発現を制御しています

機能

Sirtuin 1 はインスリン抵抗性になっている細胞において活性化が低下しています。Furthermore, SIRT1は PGC1-alpha/ERR-alpha complex, の転写因子を脱アセチル化して活性化します。

基礎実験レベルでは SIRT1 は p53 proteinを脱アセチル化し不活化します。またTh17リンパ球を活性化します。

Activators

• Lamin A is a protein that had been identified as a direct activator of Sirtuin 1 during a study on progeria.^[15]
• Resveratrol increases the expression of SIRT1, meaning that it does increase the activity of SIRT1, though not necessarily by direct activation.However, resveratrol was later shown to directly activate Sirtuin 1 against non-modified peptide substrates.
• Resveratrol also enhances the binding between Sirtuin 1 and Lamin A.
• In addition to resveratrol, a range of other plant-derived polyphenols have also been shown to interact with SIRT1.^[21]
• Metformin activates both PRKA and SIRT1.
• Although neither resveratrol or SRT1720 directly activate SIRT1, resveratrol, and probably SRT1720, indirectly activate SIRT1 by activation of AMP-activated protein kinase (AMPK),^[25] which increases NAD+ levels (which is the cofactor required for SIRT1 activity).^[26][27] 
• Elevating NAD+ is a more direct and reliable way to activate SIRT1.

Sirtuins act primarily by removing acetyl groups from lysine residues within proteins in the presence of NAD⁺

; thus, they are classified as "NAD⁺-dependent deacetylases" 

They add the acetyl group from the protein to the ADP-ribose component of NAD⁺ to form O-acetyl-ADP-ribose.

The HDAC activity of Sir2 results in tighter packaging of chromatin and a reduction in transcription at the targeted gene locus.

The silencing activity of Sir2 is most prominent at telomeric sequences

Limited overexpression of the Sir2 gene results in a lifespan extension of about 30%,^[38] if the lifespan is measured as the number of cell divisions the mother cell can undergo before cell death. Concordantly, deletion of Sir2 results in a 50% reduction in lifespan.^[38] In particular, the silencing activity of Sir2, in complex with Sir3 and Sir4, at the HM loci prevents simultaneous expression of both mating factors which can cause sterility and shortened lifespan.^[39] Additionally, Sir2 activity at the rDNA locus is correlated with a decrease in the formation of rDNA circles. Chromatin silencing, as a result of Sir2 activity, reduces homologous recombination between rDNA repeats, which is the process leading to the formation of rDNA circles. As accumulation of these rDNA circles is the primary way in which yeast are believed to "age", then the action of Sir2 in preventing accumulation of these rDNA circles is a necessary factor in yeast longevity.^[39]

Starving of yeast cells leads to a similarly extended lifespan, and indeed starving increases the available amount of NAD⁺ and reduces nicotinamide, both of which have the potential to increase the activity of Sir2. Furthermore, removing the Sir2 gene eliminates the life-extending effect of caloric restriction.^[40] Experiments in the nematode Caenorhabditis elegans and in the fruit fly Drosophila melanogaster^[41] support these findings. As of 2006, experiments in mice are underway.^[31]

However, some other findings call the above interpretation into question. If one measures the lifespan of a yeast cell as the amount of time it can live in a non-dividing stage, then silencing the Sir2 gene actually increases lifespan ^[42] Furthermore, calorie restriction can substantially prolong reproductive lifespan in yeast even in the absence of Sir2.^[43]

In organisms more complicated than yeast, it appears that Sir2 acts by deacetylation of several other proteins besides histones.

In the fruit fly Drosophila melanogaster, the Sir2 gene does not seem to be essential; loss of a sirtuin gene has only very subtle effects.^[40] However, mice lacking the SIRT1 gene (the sir2 biological equivalent) were smaller than normal at birth, often died early or became sterile.^[44]

Inhibition of SIRT1

Human aging is characterized by a chronic, low-grade inflammation level,^[45] and the pro-inflammatory transcription factor NF-κB is the main transcriptional regulator of genes related to inflammation.^[46] SIRT1 inhibits NF-κB-regulated gene expression by deacetylating the RelA/p65 subunit of NF-κB at lysine 310.^[47][48] But NF-κB more strongly inhibits SIRT1. NF-κB increases the levels of the microRNA miR-34a (which inhibits nicotinamide adenine dinucleotide NAD+ synthesis) by binding to its promoter region.^[49] resulting in lower levels of SIRT1.

Both the SIRT1 enzyme and the poly ADP-ribose polymerase 1 (PARP1) enzyme require NAD+ for activation.^[50] PARP1 is a DNA repair enzyme, so in conditions of high DNA damage, NAD+ levels can be reduced 20–30% thereby reducing SIRT1 activity.^[50]

Homologous recombination

SIRT1 protein actively promotes homologous recombination (HR) in human cells, and likely promotes recombinational repair of DNA breaks.^[51] SIRT1-mediated HR requires the WRN protein.^[51] WRN protein functions in double-strand break repair by HR.^[52] WRN protein is a RecQ helicase, and in its mutated form gives rise to Werner syndrome, a genetic condition in humans characterized by numerous features of premature aging. These findings link SIRT1 function to HR, a DNA repair process that is likely necessary for maintaining the integrity of the genome during aging.^[51]