CBP/cycA, a CCAAT-binding protein necessary for adhesion-dependent cyclin A transcription, consists of NF-Y and a novel Mr 115,000 subunit.
Cells of most tissues, with the exception of hematopoietic cells, require adhesion to an appropriate surface to grow. Cyclin A is needed for cell cycle progression at the G1-S transition, and appearance of cyclin A mRNA and protein in late G1 has been shown to be dependent on adhesion-initiated signals in normal rat kidney fibroblasts. Previously, we have reported that the adhesion-dependent activation of cyclin A transcription in late G1 is mediated by CBP/cycA (CCAAT-binding protein for cyclin A gene), a novel CCAAT-binding protein. Specific binding of CBP/cycA, a Mr 30,000/40,000/115,000 heterotrimeric protein complex, to the CCAAT element of the cyclin A promoter was detectable in growing but not in G0-arrested or nonadherent normal rat kidney cells. Here, we demonstrate that the Mr 30,000/40,000 subunits of CBP/cycA are identical with NF-YA and NF-YB, the two subunits of NF-Y. In addition, we show that, aside from CBP/cycA, NF-Y itself also binds to the CCAAT element of the cyclin A promoter. But, whereas the binding of CBP/cycA is adhesion and cell cycle dependent and correlates with the expression of cyclin A in late G1 phase, NF-Y itself seems to bind in a cell cycle-independent manner.
Krämer
A
A
III. Medizinische Klinik, Klinikum Mannheim der Universität Heidelberg, Germany.
Carstens
C P
CP
Wasserman
W W
WW
Fahl
W E
WE
D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins; D002448:Cell Adhesion; D002453:Cell Cycle; D002846:Chromatography, Affinity; D019925:Cyclin A / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D008970:Molecular Weight; D051381:Rats; D015533:Transcriptional Activation
D022762:CCAAT-Enhancer-Binding Proteins; D019925:Cyclin A; D004268:DNA-Binding Proteins