Transactivation of cytosolic alanine aminotransferase gene promoter by p300 and c-Myb.
Alanine aminotransferase (Alt) provides a molecular link between carbohydrate and amino acid metabolism. In the cell context, the predominant Alt isozyme is located in the cytosol. To gain insight into the transcriptional regulation of the cytosolic alt gene (calt), we cloned and characterized the calt promoter from gilthead sea bream (Sparus aurata). Transient transfection of sea bass larvae cells with deleted calt promoter constructs and electrophoretic mobility shift assays allowed us to identify p300 and c-Myb as new factors in the transcriptional regulation of calt expression. Transfection studies carried out with an acetylase-deficient mutant p300 (p300DY) revealed that the acetyltransferase activity of p300 is essential for the p300-mediated transcriptional activation of S. aurata calt. We had previously found up-regulation of liver cAlt2, an alternatively spliced isoform of calt, under gluconeogenic conditions and in streptozotocin (STZ)-treated S. aurata. Quantitative RT-PCR assays showed that increased p300 and c-Myb mRNA levels in the liver of starved S. aurata contribute to enhancing the transcription of cAlt2. Consistently, the administration of insulin decreased both p300 and c-Myb expression. The mRNA levels of p300 and c-Myb were also analyzed in the liver of STZ-induced diabetic S. aurata. Treatment with STZ increased the expression of p300, whereas it decreased c-Myb. Our findings suggest an involvement of p300 and c-Myb in up-regulation of cAlt2 in the liver of S. aurata under starvation. In addition, these results provide evidence for a role of p300 in diabetes.
Anemaet
Ida G
IG
Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Joan XXIII s/n, 08028 Barcelona, Spain.
González
Juan Diego
JD
Salgado
María C
MC
Giralt
Marina
M
Fernández
Felipe
F
Baanante
Isabel V
IV
Metón
Isidoro
I
D024506:5' Flanking Region / Q000235:genetics; D000410:Alanine Transaminase / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D001492:Bass; D003001:Cloning, Molecular; D016384:Consensus Sequence / Q000235:genetics; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D051548:Histone Acetyltransferases; D007328:Insulin / Q000494:pharmacology; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000187:drug effects; D020598:Proto-Oncogene Proteins c-myb / Q000378:metabolism*; D020218:Response Elements / Q000235:genetics; D021541:Sea Bream / Q000235:genetics*; D017384:Sequence Deletion; D015533:Transcriptional Activation / Q000235:genetics*; D050880:p300-CBP Transcription Factors / Q000378:metabolism*
D007328:Insulin; D046912:Multiprotein Complexes; D020598:Proto-Oncogene Proteins c-myb; D051548:Histone Acetyltransferases; D050880:p300-CBP Transcription Factors; D000410:Alanine Transaminase