Cell-density (cycle) dependent silencer of the rat insulin-like growth factor binding protein-2 (IGFBB-2) gene

An element,which has a negative effect on transcription has been identified in the 5'-flanking region of the rat insulin-like growth factor binding pr otein-2 (IGFBP-2) gene. This element was confirmed to be a silencer by trun cation or by linking it to a heterologous promoter. The silencer activity d isappeared in the growth-arrested BRL-3A cells at the G1/S border by high c ell density where the IGFBP-2 production is highly elevated. This observati on may represent a novel mechanism through which gene expression is control led by modulation of a silencer. Taken together, these results suggest a re gulatory link between cell growth and IGFBP-2 expression regulated by its s ilencer.