The expression, regulation and structure/function analysis of the transcription factor NGFI-A.

摘要

NGFI-A is a transcription factor encoded by an immediate early gene that was first isolated by virtue of its induction by NGF in PC12 (a rat pheochromocytoma cell line) cells. The expression of NGFI-A in JS1 rat schwannoma cells and other neural-crest derived cells was investigated. It was found that NGFI-A is constitutively expressed in JS1 cells and not induced by NGF. However, protein synthesis inhibitors induce NGFI-A in JS1 cells and in a wide variety of cell lines. To further understand the regulation of NGFI-A in JS1 schwannoma cells, the 5;The overexpression of some transcription factors can lead to cellular transformation or growth repression. Studies were conducted to test the effect of NGFI-A overexpression on cell growth. The overexpression of NGFI-A inhibits DNA synthesis in cells transiently transfected with CMV NGFI-A. However, following selection for stable transfectants, no difference in colony formation was detected between cells transfected with CMV NGFI-A and nonrecombinent control. In view of these contradictory results, the effect of NGFI-A on cell growth remains unclear.;NGFI-A is a phosphoprotein with a rapid half-life. The rapid half-life of the NGFI-A protein may serve as regulatory mechanism for tightly controlling its expression. The half-life of NGFI-A in 3T3 fibroblasts was found to be 100 to 140 minutes in log phase cells, but only 30 minutes in serum stimulated cells. NGFI-A induced by NGF in PC12 cells or by serum in 3T3 fibroblast cells is phosphorylated and migrates as a heterogeneous region on SDS-PAGE gel electrophoresis. Deleting regions of NGFI-A results in a loss of phosphorylation heterogeneity. NGFI-A is phosphorylated within the first 84 amino acids and this region contains a transcriptional activation domain of NGFI-A.