REGULATION OF FATTY-ACID SYNTHASE GENE-TRANSCRIPTION - SEQUENCES THATCONFER A POSITIVE INSULIN EFFECT AND DIFFERENTIATION-DEPENDENT EXPRESSION IN 3T3-L1 PREADIPOCYTES ARE PRESENT IN THE 332 BP PROMOTER
N. Moustaid et al., REGULATION OF FATTY-ACID SYNTHASE GENE-TRANSCRIPTION - SEQUENCES THATCONFER A POSITIVE INSULIN EFFECT AND DIFFERENTIATION-DEPENDENT EXPRESSION IN 3T3-L1 PREADIPOCYTES ARE PRESENT IN THE 332 BP PROMOTER, Biochemical journal, 292, 1993, pp. 767-772
We have previously reported induction of fatty acid synthase (FAS) gen
e expression by insulin and adipocyte differentiation in 3T3-L1 cells.
In order to identify sequences responsible for insulin regulation of
the FAS gene, chimaeric constructs containing serial deletions of the
5'-flanking region of the rat FAS gene ligated to the chloramphenicol
acetyltransferase (CAT) reporter gene were prepared and transfected in
to 3T3-LI cells. Plasmids. containing 2100 (-2100CAT), 1400 (-1400CAT)
, 1009 (-1009CAT) and 332 (-332CAT) bp of FAS 5' flanking sequences ex
hibited comparable basal CAT activities in 3T3-L1 preadipocytes. This
activity was 3-fold higher when these constructs were transiently tran
sfected into 3T3-LI adipocytes. Stably transfected 3T3-L1 cells also e
xhibited a 3-fold increase in CAT activity upon adipocyte differentiat
ion, indicating that sequences required for the differentiation-depend
ent increase in FAS expression are located within the 332 bp promoter.
Treatment with 10 nM insulin increased CAT activity by 2.1 +/- 0.2-.
2.6 +/- 0.1-, 2.0 +/- 0.2- and 1.7 +/- 0.2-fold respectively in 3T3-L1
adipocytes transiently transfected with -2100CAT, -1400CAT, -1009CAT
and -332CAT plasmids. CAT activity was increased by 3.0 +/- 0.3- and 3
.5 +/- 0.6-fold respectively by insulin treatment in adipocytes stably
transfected with -2100CAT and -1009CAT plasmids. When insulin-respons
ive H4IIE hepatoma cells were transiently transfected with -2100CAT, -
1400CAT, -1009CAT and -332CAT plasmids and then treated with 10 nM ins
ulin, CAT activity increased by 3.1-, 3.1 +/- 0.8-, 3.0 +/- 0.7- and 2
.3 +/- 0.5-fold respectively in serum-free media, and by 2.6 +/- 0.4-,
3.3 +/- 0.9-, 3.1 + 0.4- and 2.9 +/- 0.6-fold respectively in the pre
sence of 0.5 0% serum. These results indicate that sequences responsib
le for insulin regulation of FAS gene are also located within 332 bp o
f the transcription start site.