NF-Y-mediated trans-activation of the human thymidine kinase promoter is closely linked to activation of cyclin-dependent kinase

Transcriptional activation is important for the elevated expression of huma n thymidine kinase (hTK) in tumor cells. Here, we used TK(-133/+33)-lucifer ase reporter gene construct and bandshift assay to study the cis-elements i nvolved in transcriptional activation of the hTK promoter. We found that tw o CCAAT boxes at -71/-67 and -40/-36 and Sp1 binding site located at -118/- 113 were critical for maximal expression of the hTK promoter activity. As S p1-mediated activation of the hTK promoter was not detectable for the promo ter construct with double mutations at two CCAAT boxes, we proposed that NF -Y binding to the hTK promoter sequence is a requisite step for the functio nal interaction with Spl. Here, we further showed that the hTK promoter act ivity was reduced in HeLa cells transfected with p16 or p21, both of which are inhibitors of cyclin-dependent kinases (CDKs). Inhibition of the hTK pr omoter activity by p16 could be abrogated by overexpression of cyclin A, in dicating that the cyclin A activating event is more directly involved in tr anscriptional activation of the hTK promoter. We thus proposed that NF-Y-me diated activation of the hTK promoter is closely linked to the activation o f CDK2/cyclin A pathway. J. Cell. Biochem. 75:300-309, 1999. (C) 1999 Wiley -Liss, Inc.