Involvement of the GC-rich sequence and specific proteins (Sp1/Sp3) in the basal transcription activity of neurogranin gene.
Neurogranin (Ng), a neuronal protein implicated in learning and memory, contains a TATA-less promoter. Analysis of 5'-deletion mutations and site-directed mutations of the mouse Ng promoter revealed that a 258bp 5'-flanking sequence (+3 to +260) conferred the basal transcription activity, and that the GC-rich sequence (+22 to +33) served as an important determinant of the promoter activity. Transient transfection of the Sp1 expression plasmid transactivated the reporter activity in neuroblastoma N2A cells while knocking down of endogenous Sp1 expression resulted in a 2.5-fold reduction of the reporter activity in HEK 293 cells. Exogenous expression of Sp3 in HEK 293 cells, however, repressed the reporter activity by 50%. Nevertheless, by gel shift assays, Sp1 and Sp3 were not found to be responsible for the protein-DNA complexes formed by the GC-rich sequence. Moreover, a nuclear factor from the mouse brain tissues was discovered to bind to multiple AT-rich regions in Ng promoter.
Gui
Jingang
J
Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore.
Song
Yan
Y
Han
Nian-Lin R
NL
Zhou
Shu-Feng
SF
Sheu
Fwu-Shan
FS