title: cAMP prevents glucose-mediated modifications of histone H3 and recruitment of the RNA polymerase II holoenzyme to the L-PK gene promoter.
abstract: Glucose and cAMP reciprocally regulate expression of the L-type pyruvate kinase (L-PK) gene by controlling the formation of a complex containing the carbohydrate response element binding protein (ChREBP) and the coactivator CREB binding protein (CBP) on the L-PK promoter. However, the role of posttranslational histone modifications on the opposing effects of glucose and cAMP on the L-PK gene is unknown. Using the highly glucose-sensitive 832/13 rat insulinoma cell line, we demonstrated that glucose regulates acetylation and methylation of various histone residues at the L-PK gene promoter. These glucose-dependent histone modifications correlated with an increase in the recruitment and phosphorylation of RNA polymerase II (Pol II) on the L-PK gene promoter. Conversely, the cAMP agonist forskolin prevented glucose-mediated expression of the L-PK gene by decreasing the acetylation of histones H3 and H4 on the promoter, decreasing the methylation of H3-K4 on the coding region, and increasing the methylation of H3-K9 on the coding region. These changes induced by cAMP culminated with a decrease in the glucose-dependent recruitment of phosphorylated Pol II to the L-PK gene promoter. Furthermore, maneuvers that interfere with the glucose-dependent assembly of ChREBP and CBP on the L-PK promoter, such as increasing intracellular cAMP levels, overexpression of a dominant-negative form of ChREBP, and small-interfering-RNA-mediated suppression of CBP abundance, all altered the acetylation and methylation of histones on the L-PK promoter, which decreased Pol II recruitment and subsequently inhibited transcriptional activation of the L-PK gene. We conclude that the effects of glucose and cAMP are mediated in part by epigenetic modulation of histones.
authors.affiliation: Department of Medicine, University of Pittsburgh, PA 15261, USA.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Burke
authors.forename: J Jason
authors.initials: JJ
authors.lastname: Collier
authors.forename: Donald K
authors.initials: DK
authors.lastname: Scott
mesh_terms: D000818:Animals; D002460:Cell Line; D005576:Colforsin / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D005786:Gene Expression Regulation; D005947:Glucose / Q000378:metabolism*; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D020035:Holoenzymes / Q000235:genetics / Q000378:metabolism*; D008745:Methylation; D011401:Promoter Regions, Genetic; D011770:Pyruvate Kinase / Q000235:genetics / Q000378:metabolism; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000502:physiology
chemical_list: D006657:Histones; D020035:Holoenzymes; D034741:RNA, Small Interfering; D005576:Colforsin; D000242:Cyclic AMP; D011770:Pyruvate Kinase; D012319:RNA Polymerase II; D005947:Glucose