Enzymes in the NAD+ Salvage Pathway Regulate SIRT1 Activity at Target Gene Promoters

Abstract

In mammals, nic o tin a mide phosphoribosyltransferase (NAMPT) and nic o tin a mide mononucleotide ad en y lyltransferase 1 (NMNAT-1) constitute a nuclear NAD+ salvage pathway which regulates the functions of NAD+-de pend ent enzymes such as the protein deacetylase SIRT1. One of the major functions of SIRT1 is to regulate target gene transcription through modification of chromatin-associated proteins. However, little is known about the molecular mechanisms by which NAD+ biosynthetic enzymes regulate SIRT1 activity to control gene transcription in the nucleus. In this study we show that stable short hairpin RNA-mediated knockdown of NAMPT or NMNAT-1 in MCF-7 breast cancer cells reduces total cellular NAD+ levels and alters global patterns of gene expression. Furthermore, we show that SIRT1 plays a key role in mediating the gene regulatory effects of NAMPT and NMNAT-1. Specifically, we found that SIRT1 binds to the promoters of genes commonly regulated by NAMPT, NMNAT-1, and SIRT1 and that SIRT1 histone deacetylase activity is regulated by NAMPT and NMNAT-1 at these promoters. Most significantly, NMNAT-1 interacts with, and is recruited to target gene promoters by SIRT1. Collectively, our results reveal a mechanism for the direct control of SIRT1 deacetylase activity at a set of target gene promoters by NMNAT-1. This mechanism, in collaboration with NAMPT-de pend ent regulation of nuclear NAD+ production, establishes an important pathway for transcription regulation by NAD+. In mammals, nic o tin a mide phosphoribosyltransferase (NAMPT) and nic o tin a mide mononucleotide ad en y lyltransferase 1 (NMNAT-1) constitute a nuclear NAD+ salvage pathway which regulates the functions of NAD+-de pend ent enzymes such as the protein deacetylase SIRT1. One of the major functions of SIRT1 is to regulate target gene transcription through modification of chromatin-associated proteins. However, little is known about the molecular mechanisms by which NAD+ biosynthetic enzymes regulate SIRT1 activity to control gene transcription in the nucleus. In this study we show that stable short hairpin RNA-mediated knockdown of NAMPT or NMNAT-1 in MCF-7 breast cancer cells reduces total cellular NAD+ levels and alters global patterns of gene expression. Furthermore, we show that SIRT1 plays a key role in mediating the gene regulatory effects of NAMPT and NMNAT-1. Specifically, we found that SIRT1 binds to the promoters of genes commonly regulated by NAMPT, NMNAT-1, and SIRT1 and that SIRT1 histone deacetylase activity is regulated by NAMPT and NMNAT-1 at these promoters. Most significantly, NMNAT-1 interacts with, and is recruited to target gene promoters by SIRT1. Collectively, our results reveal a mechanism for the direct control of SIRT1 deacetylase activity at a set of target gene promoters by NMNAT-1. This mechanism, in collaboration with NAMPT-de pend ent regulation of nuclear NAD+ production, establishes an important pathway for transcription regulation by NAD+. Nicotinamide adenine dinucleotide (NAD+), a coenzyme in metabolic processes and redox reactions, is an important signaling molecule. NAD+ is (i) a substrate for mono- and poly-ADP-ribosylation of proteins, (ii) required for NAD+-dependent protein deacetylation, and (iii) a precursor for calcium mobilizing agents (1Berger F. Ramírez-Hernández M.H. Ziegler M. Trends Biochem. Sci. 2004; 29: 111-118Abstract Full Text Full Text PDF PubMed Scopus (410) Google Scholar). As a signaling molecule, NAD+ is consumed as a donor of ADP-ribose, releasing nicotinamide (NAM) 2The abbreviations used are: NAMnicotinamideChIPchromatin immunoprecipitationNAMPTnicotinamide phosphoribosyltransferaseNMNnicotinamide mononucleotideNMNAT-1nicotinamide mononucleotide adenylyltransferase 1qPCRquantitative real-time PCRRTreverse transcriptionPARPpoly(ADP-ribose) polymeraseGOgene ontologyGSTglutathione S-transferaseshRNAshort hairpin RNAHPLChigh performance liquid chromatographyLucluciferase. 2The abbreviations used are: NAMnicotinamideChIPchromatin immunoprecipitationNAMPTnicotinamide phosphoribosyltransferaseNMNnicotinamide mononucleotideNMNAT-1nicotinamide mononucleotide adenylyltransferase 1qPCRquantitative real-time PCRRTreverse transcriptionPARPpoly(ADP-ribose) polymeraseGOgene ontologyGSTglutathione S-transferaseshRNAshort hairpin RNAHPLChigh performance liquid chromatographyLucluciferase. as a byproduct. Consequently, resynthesis of NAD+ is crucial for maintaining the functions of a wide variety of NAD+-dependent enzymes in the cytoplasm and nucleus. nicotinamide chromatin immunoprecipitation nicotinamide phosphoribosyltransferase nicotinamide mononucleotide nicotinamide mononucleotide adenylyltransferase 1 quantitative real-time PCR reverse transcription poly(ADP-ribose) polymerase gene ontology glutathione S-transferase short hairpin RNA high performance liquid chromatography luciferase. nicotinamide chromatin immunoprecipitation nicotinamide phosphoribosyltransferase nicotinamide mononucleotide nicotinamide mononucleotide adenylyltransferase 1 quantitative real-time PCR reverse transcription poly(ADP-ribose) polymerase gene ontology glutathione S-transferase short hairpin RNA high performance liquid chromatography luciferase. In mammalian cells the enzymes nicotinamide phosphoribosyltransferase (NAMPT) and nicotinamide mononucleotide adenylyltransferase (NMNAT) constitute an NAD+ salvage/recycling pathway using NAM as the precursor (see Fig. 1A) (2Rongvaux A. Andris F. Van Gool F. Leo O. BioEssays. 2003; 25: 683-690Crossref PubMed Scopus (229) Google Scholar). NAMPT, a unique enzyme encoded by a single gene, catalyzes the conversion of NAM to nicotinamide mononucleotide (NMN). NAMPT localizes to both the cytosol and nucleus (3Rongvaux A. Shea R.J. Mulks M.H. Gigot D. Urbain J. Leo O. Andris F. Eur. J. Immunol. 2002; 32: 3225-3234Crossref PubMed Scopus (476) Google Scholar, 4Kitani T. Okuno S. Fujisawa H. FEBS Lett. 2003; 544: 74-78Crossref PubMed Scopus (157) Google Scholar). 3K. M. Frizzell and W. L. Kraus, unpublished information. 3K. M. Frizzell and W. L. Kraus, unpublished information. Interestingly, an extracellular form of NAMPT has also been described, although controversy exists regarding its function (5Imai S.I. Cell Biochem. Biophys. 2009; 53: 65-74Crossref PubMed Scopus (157) Google Scholar, 6Garten A. Petzold S. Körner A. Imai S. Kiess W. Trends Endocrinol. Metab. 2009; 20: 130-138Abstract Full Text Full Text PDF PubMed Scopus (312) Google Scholar). NMN produced by NAMPT is further converted into NAD+ by NMNAT. Three NMNAT enzymes encoded by distinct genes are found in mammals (7Emanuelli M. Carnevali F. Saccucci F. Pierella F. Amici A. Raffaelli N. Magni G. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, N. L. Amici A. M. F. Magni G. Biochem. Biophys. 2002; PubMed Scopus Google Scholar, M. F. M. M. T. Ziegler M. FEBS Lett. 2001; PubMed Scopus Google Scholar, S. Biochem. J. 2004; PubMed Scopus Google Scholar). NMNAT-1 is in the and are found in the and F. M. Ziegler M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). In the NAMPT and NMNAT-1 form a nuclear NAD+ salvage pathway that NAD+ as a substrate for a variety of NAD+-dependent the protein deacetylase SIRT1 and the poly(ADP-ribose) polymerase the functions of NAMPT Imai S. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, H. T. T. A. Full Text Full Text PDF PubMed Scopus Google Scholar, N. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, D. PubMed Scopus Google Scholar, Körner A. A. T. A. J. Kiess W. Imai S. Cell Metab. Full Text Full Text PDF PubMed Scopus Google Scholar, M. Full Text Full Text PDF PubMed Scopus Google Scholar, M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). found that NAMPT is regulated by and in a of and H. T. T. A. Full Text Full Text PDF PubMed Scopus Google Scholar). NAMPT levels cells through regulation of NAD+ levels and and functions in H. T. T. A. 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However, the regulatory that at gene promoters in to NAD+ are In this study we the target genes regulated by the mammalian NAD+ salvage pathway and the molecular mechanism that the NAD+ biosynthetic enzymes to results reveal a mechanism for the direct control of SIRT1 deacetylase activity at a set of target gene promoters by NMNAT-1, in collaboration with NAMPT 1 NMNAT-1 by Ziegler of NAMPT and NMNAT-1 with an and into for in mammalian and RNA of NMNAT-1 and NAMPT by NMNAT-1 also into the a for of a protein and a with an for of a PCR by SIRT1 with an as Endocrinol. 20: PubMed Scopus Google Scholar). NMNAT-1 and SIRT1 and and for RNA knockdown using the and into target for gene, and the used for the NAMPT, and NMNAT-1, and and used as a control A. D. S. A. 2004; PubMed Scopus Google Scholar). MCF-7 cells by of and in with and cells in with a using the and the of used to MCF-7 which with or as for and knockdown by of NAD+ in MCF-7 cells using a quantitative with H. T. T. A. Full Text Full Text PDF PubMed Scopus Google Scholar, T. J. PubMed Scopus Google Scholar). knockdown target for the NAMPT, NMNAT-1, and and of MCF-7 cells with NMNAT-1, NAMPT, and SIRT1 and its RNA the MCF-7 using by and to and at the using to and the of the by for effects using a A. PubMed Scopus Google Scholar). this to and the for and for in at of the for further to the to genes knockdown and the of to the gene of or to regulated gene gene for of using the and the the using RNA using by reverse transcription with an and by real-time PCR used as the of the used are using MCF-7 cells as M. T. Biol. PubMed Scopus (157) Google Scholar, Frizzell M. PubMed Scopus Google Scholar). by real-time PCR of the used are for used in this study are at are of the control as in the protein in and for for and in and using by using as a nuclear with or the and the by NAMPT and NMNAT-1 in the nuclear NAD+ salvage pathway that NAD+ using NAM the functions of NAMPT and NMNAT-1 in gene we in NAD+ and gene in MCF-7 breast cancer stable knockdown NAMPT and NMNAT-1 protein levels to of the levels in control knockdown cells cellular NAD+ levels in control and knockdown cells using a quantitative with H. T. T. A. Full Text Full Text PDF PubMed Scopus Google Scholar, T. J. PubMed Scopus Google Scholar). this we a in the total cellular NAD+ levels knockdown of NAMPT or NMNAT-1 results that both NAMPT and NMNAT-1 to NAD+ in MCF-7 that are NMNAT enzymes in in and in F. M. Ziegler M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google our results NMNAT-1 as a major to cellular NAD+ using the MCF-7 knockdown that both NAMPT and NMNAT-1 effects gene as as of the MCF-7 at or as as with a or and the and of regulation by NAMPT and NMNAT-1 in our study are in with these enzymes Imai S. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, S. S. PubMed Scopus Google Scholar). Interestingly, we an the and gene and the enzymes in and the metabolic as a of enzyme regulation of the in the or with and the and genes distinct cellular and molecular functions the commonly regulated NAMPT and NMNAT-1 target an of to and cellular functions that these functions are to of the nuclear NAD+ salvage that regulation by the used in our is to we an for NAMPT and NMNAT-1 Fig. In the effects the of genes Fig. Furthermore, we a the of protein knockdown and the effects by the Fig. results that effects a major the of target genes in our using the NAMPT and NMNAT-1 the of this we the commonly regulated NAMPT and NMNAT-1 target genes with a or genes Fig. as are to genes regulated by the salvage pathway of NAMPT and NMNAT-1. As the and of of these by NAMPT or NMNAT-1 and by NAMPT or NMNAT-1 also Fig. this regulation we the of NAD+ to the as F. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). with 1 NAD+ for the of and in the NAMPT and NMNAT-1 knockdown cells genes the of NAD+ to in the NAMPT and NMNAT-1 knockdown cells Fig. functions of NAMPT and NMNAT-1 in the regulation of target the genes to NAD+ we further NAMPT and NMNAT-1 activity is required for the regulation of these RNA of the NAD+ biosynthetic enzymes in the knockdown the enzymes the of and in the knockdown cells Fig. In the Fig. This the role of NAD+ in the regulation of these our NAD+ and enzyme for a of the and cellular NAD+ plays a direct role in the regulation of expression. the NAD+ for the of and and we the of an NAD+-dependent nuclear SIRT1 regulates a variety of cellular and and S. D. Biochem. J. PubMed Scopus Google Scholar). In MCF-7 SIRT1 activity of of protein and H. M. M. M. M. 25: PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). SIRT1 NAD+-dependent activity the of and nuclear proteins, a variety of transcription S. D. Biochem. J. PubMed Scopus Google Scholar). that SIRT1 regulates cellular of NAMPT and NMNAT-1 Imai S. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, N. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, M. Full Text Full Text PDF PubMed Scopus Google Scholar, M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, T. J. 2004; PubMed Scopus Google Scholar). Interestingly, in MCF-7 cells SIRT1 effects the of and as of NAMPT and NMNAT-1 and Furthermore, although NAD+ the of and in or little these genes in cells results that SIRT1 is required for the NAD+-dependent regulation of these further the gene regulation by SIRT1 and gene regulation by NAMPT or NMNAT-1, we an SIRT1 knockdown a control knockdown in MCF-7 of SIRT1 the of genes or with of and genes and In the used in our SIRT1 knockdown produced effects gene Fig. that effects a major the of SIRT1 target genes in our important functions of the genes in signaling and of the or genes are regulated and of by SIRT1 and the show in the knockdown cells and of the genes commonly regulated by NMNAT-1 and NAMPT or by SIRT1 Fig. an that we by these results that SIRT1 is a key of and genes commonly regulated by NAMPT, NMNAT-1, and SIRT1 are in and the cellular functions that are by the NAD+-dependent SIRT1 that of these genes in signaling functions and function in signaling and also functions (see 1 and the Furthermore, and signaling and are with of the results that the pathway and NAD+-dependent SIRT1 activity important of signaling and Interestingly, functions been for NMNAT and SIRT1 T. 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Full Text Full Text PDF PubMed Scopus Google Scholar). functions of these in gene regulation in a is with signaling functions that are commonly regulated by NAMPT, NMNAT-1, and SIRT1 in MCF-7 in the gene to protein is a of an that with in and regulates also with precursor protein and regulates a protein that protein is a for of the in the mammalian is an gene protein functions in by with of the is in the of and 1 in a of signaling protein signaling through with the of In the regulates and pathway a that regulates the pathway of protein is in and with a that regulates and modification in in binds to and in a we NAMPT, NMNAT-1, and SIRT1 at commonly regulated gene promoters. our to these genes are of regulation by the NAD+ salvage pathway as as NAD+-dependent SIRT1 the of SIRT1 to target gene with of target and transcription M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, S. D. Biochem. J. PubMed Scopus Google Scholar, J. Cell Biol. 20: PubMed Scopus Google Scholar, S. M. J. A. J. A. A. Full Text Full Text PDF PubMed Scopus Google Scholar). also of SIRT1 to the target genes that we in our in MCF-7 As in the in Fig. SIRT1 at the promoters of and of SIRT1 at the of a gene, and SIRT1 to levels SIRT1 the of the in this One of SIRT1 activity is the of histone at a modification by A. D. PubMed Scopus Google Scholar). that levels at gene although in the of genes as A. S. W. PubMed Scopus Google Scholar). and that SIRT1 is also found in at target gene promoters Fig. S. M. J. A. J. A. A. Full Text Full Text PDF PubMed Scopus Google Scholar). these we our of levels at of target genes as an of SIRT1 knockdown of SIRT1 or of SIRT1 activity with the D. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus (476) Google the levels of to total histone at the promoters of the target genes and for and for of regulation for these Interestingly, knockdown of NAMPT or NMNAT-1 effects and with to the levels of and In gene regulated by SIRT1 (i) for SIRT1 activity for by Fig. (ii) of SIRT1 knockdown or the levels of and (iii) of NAMPT or NMNAT-1 knockdown the levels of As the gene by of the As a of SIRT1 protein to these gene promoters by knockdown of NAMPT or NMNAT-1 Fig. NAMPT and NMNAT-1 control of and regulation of target genes SIRT1 activity and target genes regulated of SIRT1 activity NAMPT and NMNAT-1 control gene through mechanisms NAD+ NAD+-dependent enzymes such as Cell Biol. 20: PubMed Scopus Google NAD+-dependent transcription regulation of these these results that NAMPT and NMNAT-1 regulate molecular at target genes by SIRT1 activity through the of NAD+. results a mechanism in which NAD+ by NAMPT and NMNAT-1 regulates gene through of SIRT1 activity at target gene promoters. that both NAMPT and NMNAT-1 are found in the nucleus (3Rongvaux A. Shea R.J. Mulks M.H. Gigot D. Urbain J. Leo O. Andris F. Eur. J. Immunol. 2002; 32: 3225-3234Crossref PubMed Scopus (476) Google Scholar, 4Kitani T. Okuno S. Fujisawa H. FEBS Lett. 2003; 544: 74-78Crossref PubMed Scopus (157) Google Scholar, F. M. Ziegler M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google we the that recruited to the promoters of target genes for in a to SIRT1. this we the of NAMPT and NMNAT-1 to target gene promoters in MCF-7 cells NAMPT or NMNAT-1. NMNAT-1 at the promoters of the commonly regulated target genes and at and of the genes or at the of a gene and Fig. the we to NAMPT at the promoters the that the our in the chromatin of NMNAT-1 and NAMPT an important cellular the of NMNAT-1 and SIRT1 to the we the that SIRT1 NMNAT-1 to knockdown of SIRT1 the of NMNAT-1 to target gene promoters Furthermore, our SIRT1 with and in the proteins. In an in SIRT1 in nuclear to these results that SIRT1 binds to and NMNAT-1 to In this study we the gene regulatory function of enzymes in the nuclear NAD+ biosynthetic NAMPT and NMNAT-1, as as the nuclear NAD+-dependent protein SIRT1. knockdown and we a set of genes commonly regulated by NAMPT, NMNAT-1, and SIRT1 in MCF-7 we that SIRT1 binds to the of these we the of SIRT1 in our that SIRT1 recruited to gene promoters through direct with transcription as as transcription M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, J. Cell Biol. 20: PubMed Scopus Google Scholar). In our study we that the deacetylase activity of SIRT1 at target gene promoters is by NAMPT and NMNAT-1, mechanism for NAMPT and transcription Interestingly, we found that NMNAT-1 is recruited to target gene promoters through with SIRT1. This of NMNAT-1 and SIRT1 chromatin a unique mechanism for NAD+-dependent regulation our is that the gene regulated by NAMPT or NMNAT-1 show a Fig. and enzymes are in a NAD+ biosynthetic and knockdown effects cellular NAD+ levels genes that are regulated by nuclear NAD+ levels are to to both enzymes in a However, both NAMPT and NMNAT-1 gene regulatory of NAD+ in the nucleus. NAMPT is found in (3Rongvaux A. Shea R.J. Mulks M.H. Gigot D. Urbain J. Leo O. Andris F. Eur. J. Immunol. 2002; 32: 3225-3234Crossref PubMed Scopus (476) Google Scholar, 4Kitani T. Okuno S. Fujisawa H. FEBS Lett. 2003; 544: 74-78Crossref PubMed Scopus (157) Google Scholar, H. T. T. A. Full Text Full Text PDF PubMed Scopus Google NAD+ levels and gene of the nuclear NAD+ of NAMPT activity is to NAM M. Full Text Full Text PDF PubMed Scopus Google an of and of NAM to show in total cellular NAM levels in our NAMPT or NMNAT-1 knockdown cells However, we the that effects of NAMPT gene are through NAM in a NMNAT-1 is an nuclear protein and is recruited to gene promoters interacts with nuclear such as SIRT1 and and F. Ziegler M. Sci. PubMed Scopus Google Scholar). and W. L. unpublished unique and of NMNAT-1 to gene regulation of nuclear NAD+ these for the we a of genes that are commonly regulated by NAMPT, NMNAT-1, and SIRT1 and of transcription regulation by both the NAD+ salvage pathway and SIRT1. that the cellular functions of SIRT1 are regulated by NAMPT and NMNAT-1 Imai S. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, N. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, D. PubMed Scopus Google Scholar, M. Full Text Full Text PDF PubMed Scopus Google Scholar, M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, T. J. 2004; PubMed Scopus Google Scholar). In the of NAMPT, its been to in cellular NAD+ Imai S. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, H. T. T. A. Full Text Full Text PDF PubMed Scopus Google Scholar, N. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, M. Full Text Full Text PDF PubMed Scopus Google Scholar, A. M. S. Van Gool F. F. Andris F. Leo O. J. Immunol. PubMed Scopus Google Scholar). NAMPT cellular NAM levels M. Full Text Full Text PDF PubMed Scopus Google Scholar). of these of NAMPT SIRT1 little about the molecular mechanisms by which NAMPT and NMNAT-1 regulation of target gene promoters. NAMPT the of SIRT1 in a gene Imai S. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). In SIRT1 is recruited to the of a gene through with M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). SIRT1 is by and histone to transcription NAMPT SIRT1 activity and target gene through NAD+ M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). results these to a molecular mechanism for the regulation of SIRT1 activity at target gene promoters by nuclear NAD+ biosynthetic NAMPT and NMNAT-1 regulate cellular NAD+ as as SIRT1 activity at the of target the role of NAD+ in of NMNAT-1 and SIRT1 at target gene promoters regulatory mechanisms the NMNAT-1 and SIRT1. SIRT1 an enzyme such as NMNAT-1 to target gene promoters for the of in the for NAD+ and the to of NAD+ of NMNAT-1 and SIRT1 at target gene promoters regulate SIRT1 activity in of NMNAT-1 and SIRT1 NAD+ by through a substrate mechanism Biochem. PubMed Scopus Google Scholar). In this O. FEBS J. PubMed Scopus Google that NAD+ biosynthetic enzymes form a with SIRT1 and NAD+ to a of high NAD+ for regulation of SIRT1 results in of this Interestingly, our results that a in total cellular NAD+ levels NAMPT or NMNAT-1 knockdown to as as a in levels at SIRT1 target gene promoters One for this is that the in nuclear NAD+ levels NAMPT or NMNAT-1 knockdown in the as a O. FEBS J. PubMed Scopus Google that NAD+ at the of SIRT1 total cellular NAD+ a role in SIRT1 in which the of NMNAT-1 and SIRT1 at target gene promoters regulate SIRT1 activity is to that the activity of or both as for NMNAT-1 and F. Ziegler M. Sci. PubMed Scopus Google Scholar). NMNAT-1 and SIRT1 for regulation by cellular signaling an of regulatory to the both NAD+ and SIRT1 activity are regulated by a wide of extracellular L. PubMed Google Scholar, J. PubMed Scopus Google Scholar, Biochem. PubMed Scopus Google Scholar). and cellular regulate the of NAMPT H. T. T. A. Full Text Full Text PDF PubMed Scopus Google Scholar, N. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, D. PubMed Scopus Google Scholar, M. Full Text Full Text PDF PubMed Scopus Google a enzyme in the NAD+ pathway Imai S. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). Consequently, these control NAD+ through regulation of NMN protein control the NMNAT-1 and enzymes F. Ziegler M. Sci. PubMed Scopus Google to regulation of NMNAT-1 to results that the these signaling is to an important in NAD+ and regulation at target gene promoters. of by nuclear metabolic enzymes for by or enzymes is an by a nuclear in the has been to regulate the activity of histone H. Full Text Full Text PDF PubMed Scopus Google Scholar). to which and metabolic enzymes NMNAT-1, recruited to target gene promoters has to this of a and mechanism for with