Identification of the Serum-Responsive Transcription Initiation Site of the Zinc Finger Gene Krox-20

The Krox-20 gene is rapidly and transiently induced when quiescent 3T3 cells are stimulated to reenter the proliferative cycle. We identified the major serum-responsive transcription initiation site and found that it differs from the initiation sites previously identified for the Krox-20 gene. Transcripts from the major serum-responsive initiation site increased at least 40-fold in serum-stimulated cells compared with logarithmically growing cells.