RESUMO
In this study we investigated the effect of histone acetylation on the transcription of adrenergic-induced genes in rat pinealocytes. We found that treatment of pinealocytes with trichostatin A (TSA), a histone deacetylase inhibitor, caused hyperacetylation of histone H3 (H3) Lys14 at nanomolar concentrations. Hyperacetylation of H3 was also observed after treatment with scriptaid, a structurally unrelated histone deacetylase inhibitor. The effects of TSA and scriptaid were inhibitory on the adrenergic induction of arylalkylamine-n-acetyltransferase (aa-nat) mRNA, protein, and enzyme activity, and on melatonin production. TSA at higher concentrations also inhibited the adrenergic induction of mapk phosphatase-1 (mkp-1) and inducible cAMP early repressor mRNAs. In contrast, the effect of TSA on the norepinephrine induction of the c-fos mRNA was stimulatory. Moreover, the effect of TSA on adrenergic-induced gene transcription was dependent on the time of its addition; its effect was only observed during the active phase of transcription. Chromatin immunoprecipitation with antibodies against acetylated Lys14 of H3 showed an increase in DNA recovery of the promoter regions of aa-nat, mkp-1, and c-fos after treatment with TSA. Together, our results demonstrate that histone acetylation differentially influences the transcription of adrenergic-induced genes, an enhancing effect for c-fos but inhibitory for aa-nat, mkp-1, and inducible cAMP early repressor. Moreover, both inhibitory and enhancing effects appear to be mediated through specific modification of promoter-bound histones during gene transcription.
Assuntos
Adrenérgicos/farmacologia , Histonas/metabolismo , Glândula Pineal/metabolismo , Transcrição Gênica/efeitos dos fármacos , Acetilação , Agonistas alfa-Adrenérgicos/administração & dosagem , Agonistas alfa-Adrenérgicos/farmacologia , Animais , Arilalquilamina N-Acetiltransferase/antagonistas & inibidores , Arilalquilamina N-Acetiltransferase/genética , Arilalquilamina N-Acetiltransferase/metabolismo , Proteínas de Ciclo Celular/genética , Células Cultivadas , Modulador de Elemento de Resposta do AMP Cíclico/genética , Esquema de Medicação , Fosfatase 1 de Especificidade Dupla , Inibidores Enzimáticos/administração & dosagem , Inibidores Enzimáticos/farmacologia , Inibidores de Histona Desacetilases , Ácidos Hidroxâmicos/administração & dosagem , Ácidos Hidroxâmicos/farmacologia , Hidroxilaminas/farmacologia , Proteínas Imediatamente Precoces/genética , Melatonina/biossíntese , Norepinefrina/administração & dosagem , Norepinefrina/farmacologia , Fosfoproteínas Fosfatases/genética , Glândula Pineal/citologia , Proteína Fosfatase 1 , Proteínas Tirosina Fosfatases/genética , Proteínas Proto-Oncogênicas c-fos/genética , Quinolinas/farmacologia , RNA Mensageiro/antagonistas & inibidores , RNA Mensageiro/metabolismo , RatosRESUMO
In this study, we investigated phosphorylation of Ser10 in histone H3 by norepinephrine (NE) in the rat pineal gland. In whole-animal studies, we demonstrated a marked increase in histone H3 phosphorylation in the rat pineal gland during the first half of the dark period. Exposure to light during this period caused a rapid decline in histone H3 phosphorylation with an estimated t1/2 of less than 15 min, indicating a high level of dephosphorylation activity. Corresponding studies in cultured pineal cells revealed that treatment with NE produced an increase in histone H3 phosphorylation that peaked between 2 and 3 h and declined rapidly by 4 h. The NE-induced histone H3 phosphorylation was blocked by cotreatment with propranolol or KT5720, a protein kinase A inhibitor, but not by prazosin or other kinase inhibitors. Moreover, only treatment with dibutyryl cAMP but not other kinase activators mimicked the effect of NE on histone H3 phosphorylation. The NE-stimulated H3 phosphorylation was markedly increased by cotreatment with a serine/threonine phosphatase inhibitor, tautomycin or okadaic acid, supporting a high level of ongoing histone H3 dephosphorylation activity. Together, our results indicate that histone H3 phosphorylation is a naturally occurring event at night in the rat pineal gland that is driven almost exclusively by a NE-->beta-adrenergic-->cAMP/protein kinase A signaling mechanism. This transient histone H3 phosphorylation probably reflects the nocturnal activation of multiple adrenergic-regulated genes in the rat pineal gland.