The growth-dependent expression of the adenine nucleotide translocase-2 (ANT2) gene is regulated at the level of transcription and is a marker of cell proliferation

The adenine nucleotide translocator-2 (ANTS) gene is expressed in growth-ac tivated cells together with the early-immediate genes. We have studied the mechanism of ANTS expression during the serum-induced transition from G0 to G1 and during reentry into G0 as cells approach confluence. Actinomycin D completely blocked ANTS expression of serum-induced quiescent NIH3T3. In ad dition, no serum-dependent changes were observed in the stability of ANT2 t ranscripts in cells activated by serum or during the breakdown of transcrip ts caused by serum removal and reentry into G0. Thus, all changes in ANTS t ranscript levels appear to be regulated predominantly at the level of trans cription. Using cells permanently transfected with deletion constructs of t he ANTE promoter, we identified a suppressor region that is responsible for decreased expression of ANTS in cells leaving the growth cycle at confluen ce. Thus, ANTE is expressed during the proliferation state via a mechanism that most probably includes transcription repression/derepression. (C) 1999 Academic Press.