Identification of BTG2, an antiproliferative p53–dependent component of the DNA damage cellular response pathway

Cell cycle regulation is critical for maintenance of genome integrity. A prominent factor that guarantees genomic stability of cells is p53 (ref. 1). The P53 gene encodes a transcription factor that has a role as a tumour suppressor2. Identification of p53-target genes should provide greater insight into the molecular mechanisms that mediate the tumour suppressor activities of p53. The rodent Pc3/Tis21 gene was initially described as an immediate early gene induced by tumour promoters and growth factors in PC12 and Swiss 3T3 cells3,4. It is expressed in a variety of cell and tissue types and encodes a remarkably labile protein4,5. Pc3/Tis21 has a strong sequence similarity to the human antiproliferative BTG1 gene cloned from a chromosomal transloca-tion of a B-cell chronic lymphocytic leukaemia6. This similarity led us to speculate that BTG1 and the putative human homologue of Pc3/Tis21 (named BTG2) were members of a new family of genes involved in growth control and/or differentiation. This hypothesis was recently strengthened by the identification of a new antiproliferative protein, named TOB, which shares sequence similarity with BTG1 and PC3/TIS21 (ref. 7). Here, we cloned and localized the human BTG2 gene. We show that BTG2 expression is induced through a p53-depen-dent mechanism and that BTG2 function may be relevant to cell cycle control and cellular response to DNA damage.