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J Am Chem Soc. 2019 Feb 13;141(6):2462-2473. doi: 10.1021/jacs.8b12083. Epub 2019 Feb 4.

A Click Chemistry Approach Reveals the Chromatin-Dependent Histone H3K36 Deacylase Nature of SIRT7.

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Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States.
Department of Medicine , Stanford University School of Medicine , Stanford , California 94305 , United States.
Division of Biostatistics, Dan L. Duncan Cancer Center , Baylor College of Medicine , Houston , Texas 77030 , United States.
Howard Hughes Medical Institute, Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States.
Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China.
Geriatric Research, Education, and Clinical Center , Veterans Affairs Palo Alto Health Care System , Palo Alto , California 94304 , United States.


Using an engineered pyrrolysyl-tRNA synthetase mutant together with tRNACUAPyl, we have genetically encoded Nε-(7-azidoheptanoyl)-l-lysine (AzHeK) by amber codon in Escherichia coli for recombinant expression of a number of AzHeK-containing histone H3 proteins. We assembled in vitro acyl-nucleosomes from these recombinant acyl-H3 histones. All these acyl-nucleosomes contained an azide functionality that allowed quick click labeling with a strained alkyne dye for in-gel fluorescence analysis. Using these acyl-nucleosomes as substrates and click labeling as a detection method, we systematically investigated chromatin deacylation activities of SIRT7, a class III NAD+-dependent histone deacylase with roles in aging and cancer biology. Besides confirming the previously reported histone H3K18 deacylation activity, our results revealed that SIRT7 has an astonishingly high activity to catalyze deacylation of H3K36 and is also catalytically active to deacylate H3K37. We further demonstrated that this H3K36 deacylation activity is nucleosome dependent and can be significantly enhanced when appending the acyl-nucleosome substrate with a short double-stranded DNA that mimics the bridging DNA between nucleosomes in native chromatin. By overexpressing SIRT7 in human cells, we verified that SIRT7 natively removes acetylation from histone H3K36. Moreover, SIRT7-deficient cells exhibited H3K36 hyperacetylation in whole cell extracts, at rDNA sequences in nucleoli, and at select SIRT7 target loci, demonstrating the physiologic importance of SIRT7 in determining endogenous H3K36 acetylation levels. H3K36 acetylation has been detected at active gene promoters, but little is understood about its regulation and functions. Our findings establish H3K36 as a physiologic substrate of SIRT7 and implicate this modification in potential SIRT7 pathways in heterochromatin silencing and genomic stability.


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