[Regulation of transcription factors c-myb and liver activator protein on expression of alpha1(I) collagen gene in activated hepatic stellate cells].

OBJECTIVE

To elucidate the role of two transcription factors, c-myb and liver activator protein (LAP, a member of the C/EBP family) in the expression of alpha1(I) collagen gene in activated hepatic stellate cells (HSCs).

METHODS

Rat HSCs were prepared from SD rats by in situ perfusion and single-step density Nycodenz gradient. Two chimeric luciferase reporter gene plasmids containing the human collagen alpha1(I) gene promoter fragments (-804 approximately +1452 or -804 approximately +222) were constructed. Culture-activated HSCs were co-transfected with the reporter gene constructs and mammalian vectors expressing c-myb or/and LAP using the cationic-liposome mediated method.

RESULTS

Transient transfection of the vector expressing LAP significantly increased basal transcription from PGL(3)-col and PGL(3)-col (intron) reporter gene vectors [(587 +/- 62)U/mg protein vs (315 +/- 45)U/mg protein and (326 +/- 52)U vs (220 +/- 70)U, t=10.4 and 3.6, respectively, both P<0.05]. C-myb showed no transactivation to both PGL(3)-col and PGL(3)-col (intron) reporter gene vectors. But co-expression of LAP and c-myb increased basal transcription from PGL(3)-col reporter gene by approximate 3 fold (1261 +/- 130)U vs (315 +/- 45)U, t=20.6, P<0.01. Moreover, co-expression of a specific c-myb antisense vector with the LAP vector inhibited the transactivation of LAP to collagen alpha1(I) gene promoter activity (334 +/- 29)U vs (315 +/- 45)U, t=1.06, P>0.05), which was observed only in PGL(3)-col plasmids.

CONCLUSION

The transcription factor LAP transactivates collagen alpha1(I) gene in activated HSCs. C-myb plays an important role in transcriptional regulation of alpha1(I) collagen gene in HSCs and this effect is mediated by the transcription factor LAP and the cis-acting element in the first intron of alpha1(I) collagen gene.