RESUMO
BACKGROUND: Cardiac hypertrophic growth is mediated by robust changes in gene expression and changes that underlie the increase in cardiomyocyte size. The former is regulated by RNA polymerase II (pol II) de novo recruitment or loss; the latter involves incremental increases in the transcriptional elongation activity of pol II that is preassembled at the transcription start site. The differential regulation of these distinct processes by transcription factors remains unknown. Forkhead box protein O1 (FoxO1) is an insulin-sensitive transcription factor that is also regulated by hypertrophic stimuli in the heart. However, the scope of its gene regulation remains unexplored. METHODS: To address this, we performed FoxO1 chromatin immunoprecipitation-deep sequencing in mouse hearts after 7 days of isoproterenol injections (3 mg·kg-1·mg-1), transverse aortic constriction, or vehicle injection/sham surgery. RESULTS: Our data demonstrate increases in FoxO1 chromatin binding during cardiac hypertrophic growth, which positively correlate with extent of hypertrophy. To assess the role of FoxO1 on pol II dynamics and gene expression, the FoxO1 chromatin immunoprecipitation-deep sequencing results were aligned with those of pol II chromatin immunoprecipitation-deep sequencing across the chromosomal coordinates of sham- or transverse aortic constriction-operated mouse hearts. This uncovered that FoxO1 binds to the promoters of 60% of cardiac-expressed genes at baseline and 91% after transverse aortic constriction. FoxO1 binding is increased in genes regulated by pol II de novo recruitment, loss, or pause-release. In vitro, endothelin-1- and, in vivo, pressure overload-induced cardiomyocyte hypertrophic growth is prevented with FoxO1 knockdown or deletion, which was accompanied by reductions in inducible genes, including Comtd1 in vitro and Fstl1 and Uck2 in vivo. CONCLUSIONS: Together, our data suggest that FoxO1 may mediate cardiac hypertrophic growth via regulation of pol II de novo recruitment and pause-release; the latter represents the majority (59%) of FoxO1-bound, pol II-regulated genes after pressure overload. These findings demonstrate the breadth of transcriptional regulation by FoxO1 during cardiac hypertrophy, information that is essential for its therapeutic targeting.
Assuntos
Cardiomegalia/metabolismo , Proteínas Relacionadas à Folistatina/metabolismo , Proteína Forkhead Box O1/metabolismo , Uridina Quinase/metabolismo , Animais , Cardiomegalia/genética , Proteínas Relacionadas à Folistatina/genética , Proteína Forkhead Box O1/genética , Camundongos , RNA Polimerase II/genética , RNA Polimerase II/metabolismo , Uridina Quinase/genéticaRESUMO
UMPK 3 is a rare variant of the polymorphic enzyme of human red cells, uridine monophosphate kinase. This homozygote phenotype was detected among the Warao Indians of Venezuela. The UMPK 1 and UMPK 3 enzymes were partially purified following the method described by Tend et al. (1976). The biochemical and kinetic parameters of both variants were studied in crude hemolysates and in partially purified enzymes. A comparison was made with the results previously reported by Teng for UMPK 1 and UMPK 2, and it was concluded that UMPK 3 seems to resemble the other two allelic gene products in Km values for UMP, CMP, and ATP but differs from them in electrophoretic mobility, pH optimum, and thermal stability.
Assuntos
Alelos , Frequência do Gene , Indígenas Sul-Americanos , Fosfotransferases/genética , Uridina Quinase/genética , Eletroforese , Eritrócitos/enzimologia , Humanos , Concentração de Íons de Hidrogênio , Cinética , Uridina Quinase/isolamento & purificação , Uridina Monofosfato/metabolismo , VenezuelaRESUMO
A study of the uridine monophosphate kinase (UMPK) electrophoretic patterns in Venezuelan individuals from the mestizo population of Caracas and from the Warao Indians of the Nabasanuka village in the Delta of the Orinoco River are reported. Among the mestizo population, the frequency of the UMPK1, UMPK2, and UMPK3 alleles was .979, .020, and .001, respectively. A higher frequency of the UMPK3 gene was seen in the highly inbred Warao Indians than any other population studied to date.