Identification and characterization of the putative retinoblastoma controlelement of the rat insulin-like growth factor binding protein-2 gene

The authors previously identified a silencer of the rat IGFBP-2 gene. Seque nce examination of the silencer has revealed that it contains the target se quence for the pRb (retinoblastoma) tumour suppressor gene, referred to as the retinoblastoma control element (RCE) which is frequently found in the r egulatory element of cellular oncogenes and growth factors. The presence of RCE suggests that the IGFBP-2 gene may be regulated by the pRb tumour supp ressor gene. An in vitro gel retardation assay has shown that the putative RCEs from the IGFBP-2 gene are complexed with multiple nuclear factors from the rat liver BRL-3A cells. These DNA-protein complexes were not detected with the nuclear extracts from the cells that were growth arrested at the G 1/S border of the cell cycle by high cell density. Using specific antibodie s, Spl was shown to be one of the components for the multiple DNA-protein c omplex while pRb does not appear to be directly involved in the formation o f the complex. (C) 1999 Elsevier Science ireland Ltd. All rights reserved.