TY - JOUR
T1 - Localization of sequences for the basal and insulin-like growth factor-I inducible activity of the fatty acid synthase promoter in 3T3-L1 fibroblasts
AU - Misra, S.
AU - Sakamoto, K.
AU - Moustaid, N.
AU - Sul, H. S.
PY - 1994
Y1 - 1994
N2 - Fatty acid synthase (FAS) plays a central role in fatty acid synthesis and its expression is under nutritional and hormonal control. We have investigated insulin-like growth factor-I (IGF-I) regulation of FAS by transfecting into 3T3-L1 fibroblasts chimeric genes comprising the 5'-flanking region of the FAS gene linked to a luciferase (LUC) reporter gene. First, the basal promoter activity of the 5' serial deletions from nucleotides -318 to -19 of the FAS gene were compared. Deletions of the promoter sequences from -136 to -19 resulted in a step-wise decrease in the promoter activity, with the -67 LUC and -19 LUC plasmids retaining 40% and 16% of the luciferase activity of -136 LUC. Regulatory sequences important for the FAS basal promoter activity in 3T3-L1 fibroblasts are, therefore, located within the -136 to -19 region. Treatment with 10 nM IGF-I also increased luciferase activity 1.8 ± 0.2-, 1.8 ± 0.3- and 2.5 ± 0.1-fold in 3T3-L1 fibroblasts transiently transfected with -136 LUC, -110 LUC and -67 LUC plasmids, respectively. Deletion of sequences from -67 to -19 resulted in the loss of responsiveness to IGF-I. Physiological doses of insulin (10 nM), however, did not increase luciferase activity in 3T3-L1 fibroblasts transfected with any of the above plasmids. Only upon treatment with pharmacological doses of insulin (1 μM), probably through IGF-I receptor, did luciferase activity increase 4.3 ± 0.4-, 3.2 ± 0.4- and 3.5 ± 0.5-fold when transfected with -136 LUC, -110 LUC and -67 LUC plasmids, respectively, there was no increase with -19 LUC. The half-maximal effect of IGF-I on FAS promoter activity was observed at 3 nM and a maximal effect was reached at 10 nM. These results indicate that the increased promoter activities observed are probably mediated through the IGF-I receptor. Furthermore, sequences responsible for IGF-I regulation of the FAS gene are located within the proximal promoter between nucleotides 67 and 19 of the FAS gene.
AB - Fatty acid synthase (FAS) plays a central role in fatty acid synthesis and its expression is under nutritional and hormonal control. We have investigated insulin-like growth factor-I (IGF-I) regulation of FAS by transfecting into 3T3-L1 fibroblasts chimeric genes comprising the 5'-flanking region of the FAS gene linked to a luciferase (LUC) reporter gene. First, the basal promoter activity of the 5' serial deletions from nucleotides -318 to -19 of the FAS gene were compared. Deletions of the promoter sequences from -136 to -19 resulted in a step-wise decrease in the promoter activity, with the -67 LUC and -19 LUC plasmids retaining 40% and 16% of the luciferase activity of -136 LUC. Regulatory sequences important for the FAS basal promoter activity in 3T3-L1 fibroblasts are, therefore, located within the -136 to -19 region. Treatment with 10 nM IGF-I also increased luciferase activity 1.8 ± 0.2-, 1.8 ± 0.3- and 2.5 ± 0.1-fold in 3T3-L1 fibroblasts transiently transfected with -136 LUC, -110 LUC and -67 LUC plasmids, respectively. Deletion of sequences from -67 to -19 resulted in the loss of responsiveness to IGF-I. Physiological doses of insulin (10 nM), however, did not increase luciferase activity in 3T3-L1 fibroblasts transfected with any of the above plasmids. Only upon treatment with pharmacological doses of insulin (1 μM), probably through IGF-I receptor, did luciferase activity increase 4.3 ± 0.4-, 3.2 ± 0.4- and 3.5 ± 0.5-fold when transfected with -136 LUC, -110 LUC and -67 LUC plasmids, respectively, there was no increase with -19 LUC. The half-maximal effect of IGF-I on FAS promoter activity was observed at 3 nM and a maximal effect was reached at 10 nM. These results indicate that the increased promoter activities observed are probably mediated through the IGF-I receptor. Furthermore, sequences responsible for IGF-I regulation of the FAS gene are located within the proximal promoter between nucleotides 67 and 19 of the FAS gene.
UR - http://www.scopus.com/inward/record.url?scp=0028350922&partnerID=8YFLogxK
U2 - 10.1042/bj2980575
DO - 10.1042/bj2980575
M3 - Article
C2 - 7511375
AN - SCOPUS:0028350922
VL - 298
SP - 575
EP - 578
JO - Biochemical Journal
JF - Biochemical Journal
SN - 0264-6021
IS - 3
ER -