Anti-SIRT6 (C-terminal) polyclonal antibody

Chromatin structure and gene expression are dynamically regulated by posttranslational modifications of histones. Recent advance in mass spectrometry has identified novel types of lysine acylations, such as butyrylation and malonylation, whose functions and regulations are likely different from those of acetylation. Sirtuins, nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylases, catalyze various deacylations. However, it is poorly understood how distinct sirtuins regulate the histone acylation states of nucleosomes that have many lysine residues. Here, we provide mass spectrometry-based quantitative information about the acyl group-and site-selectivity of all human sirtuins on acylated nucleosomes. The acyl group-and site-selectivity of each sirtuin is unique to its subtype. Sirt5 exclusively removes negatively-charged acyl groups, while Sirt1/2/3/6/7 preferentially remove hydrophobic acyl groups; Sirt1 and Sirt3 selectively remove acetyl group more than butyryl group, whereas Sirt2 and Sirt6 showed the opposite selectivity. Investigating site-selectivity for active sirtuins revealed acylated lysines on H4 tails to be poor substrates and acylated H3K18 to be a good substrate. Furthermore, we found Sirt7 to be a robust deacylase of H3K36/37, and its activity reliant on nucleosome-binding at its C-terminal basic region. All together, our quantitative dataset provides a useful resource in understanding chromatin regulations by histone acylations.

SIRT6, NAD+-dependent deacetylase sirtuin 6, has recently shown to suppress tumor growth in several types of cancer. Colon cancer is a challenging carcinoma associated with high morbidity and death. However, whether SIRT6 play a direct role in colon tumorigenesis and the underlying mechanism are not understood. Methods: To investigate the role of SIRT6 in colon cancer, we firstly analyzed the specimens from 50 colorectal cancer (CRC) patients. We generated shSIRT6 LoVo cells and xenograft mouse to reveal the essential role of SIRT6 in cell apoptosis and tumor growth. To explore the underlying mechanism of SIRT6 regulation, we performed FRET and real-time fluorescence imaging in living cells, real-time PCR, immunoprecipitaion, immunohistochemistry, flow cytometry and luciferase reporter assay. Results: The expression level of SIRT6 in patients' specimens is lower than that of normal controls, and patients with higher SIRT6 level have a better prognosis. Here, we identified that transcriptional factor FoxO3a is a direct up-stream of SIRT6 and positively regulated SIRT6 expression, which in turn, promotes apoptosis by activating Bax and mitochondrial pathway. Functional studies reveal that Akt inactivation increases FoxO3a activity and augment its binding to SIRT6 promoter, leading to elevated SIRT6 expression. Knocking down SIRT6 abolished apoptotic responses and conferred resistance to the treatment of BKM120. Combinational therapies with conventional drugs showed synergistic chemosensitization, which was SIRT6-dependent both in vitro and in vivo. Conclusion: The results uncover SIRT6 as a new potential biomarker for colon cancer, and its unappreciated mechanism about transcription and expression via Akt/FoxO3a pathway.