Bromodomain factor 1 (Bdf1) is phosphorylated by protein kinase CK2

Bromodomain factor 1 (Bdf1) associates with Saccharomyces cerevisiae TFIID and corresponds to the C-terminal half of higher eukaryotic TAFI. It also associates with the SWR-C complex, which is important for Htzl deposition. Bdf1 binds preferentially to acetylated histone H4. Bdf1 is; phosphorylated, but the mechanism and significance of this modification have been unclear. Two distinct regions within Bdf1 are phosphorylated; one is just C terminal to the bromodomains and the other is near the C terminus. Mutational analysis shows that phosphorylation is necessary for Bdf1 function in vivo. Endogenous protein kinase CK2 purifies with Bdf1 and phosphorylates both domains. A similar mechanism may be responsible for phosphorylation of the C-terminal region of mammalian TAFI. These findings suggest that CK2 phosphorylation of Bdf1 may regulate RNA polymerase II transcription and/or chromatin structure.