Human thymidine kinase CCAAT-binding protein is NF-Y, whose A subunit expression is serum-dependent in human IMR-90 diploid fibroblasts.
The nuclear protein interacting with the distal CCAAT box of human thymidine kinase (TK) gene promoter has been suggested to be a specific TK-CCAAT-binding protein, which is responsible for the serum-dependence of TK transactivation in normal human IMR-90 fibroblasts. By biochemical characterization, TK-CCAAT-binding protein was found to be distinct from other known CCAAT-binding proteins (Pang, J. H., and Chen, K. Y. (1993) J. Biol. Chem. 268, 2909-2916). In this study, we identify NF-Y, which is composed of Ya and Yb subunits, to be responsible for the TK-CCAAT binding activity in the crude nuclear extract from HL-60 cells. The interaction of NF-Y with the distal CCAAT box of the TK promoter in the crude extract appeared to be more heat-sensitive than that in the DNA affinity chromatography purified fraction. We have further established that the serum dependence of TK-CCAAT binding activity in normal IMR-90 fibroblasts is due to the decrement of NF-Ya, but not NF-Yb expression following serum-deprivation, and that such serum dependence is absent in HL-60 cells.
Chang
Z F
ZF
Department of Biochemistry, Chang Gung College of Medicine and Technology, Tao-Yuan, Taiwan, Republic of China.
Liu
C J
CJ
D001483:Base Sequence; D001667:Binding, Competitive; D001769:Blood; D022762:CCAAT-Enhancer-Binding Proteins; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism*; D004171:Diploidy; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D013937:Thymidine Kinase / Q000235:genetics
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D004247:DNA; D013937:Thymidine Kinase