Analysis of transcriptional activation domains of eukaryotic transcription factors using yeast GAL4 fusion system

Some of eukaryotic transcription factors are multifunctional proteins which play important roles in DNA replication as well as in transcription. Two of such proteins, yeast ARS binding factor 1 (ABF1) and rat Nuclear Factor 1-A (NF1-A), were analyzed for their abilities to activate transcription in yeast cells using yeast GAL4 fusion system. Different regions of ABF1 and NF1-A were fused with yeast GAL4 DNA binding domain and monitored for transcriptional activation abilities in yeast cells. Our studies reveal that ABF1 was incapble of activating transcription in yeast by itself, indicating that ABF1 may require some other factors for activation of transcription. In contrast, rat NF1-A was able to activate transcription in yeast, indicating that NF1-A activates transcription by direct interaction with some components of transcription machinery which were conserved among wide ranges of cells. Two domains in rat NF1-A between amino acid residues 393 and 447 and between residues 448 and 509, were important for transcriptional activation functions The carboxyterminal region of NF1-A at the position between residues 470 and 482 contains SPTSPTY sequence similar to the heptapeptide of carboxyterminal domain (CTD) of RNA polymerase ii largest subunit, which has been implicated in the activation of transcription previously. The two domains were able to activate transcription independently and, when present together, more active than each of the domains by about two folds.