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The TATA box-binding factor TFIID mediates transcriptional regulation through interactions with various regulatory factors and putative participation in reconfiguration of nucleosomes, utilizing its components, which include TATA box-binding protein (TBP) and TBP-associated factors (TAFs). Our and other previous studies have elucidated that there exist histone-similar TAFs. Studies on TAFs similar to histone H3 and H4 have revealed their biochemical and structural similarities to the corresponding histones. However, the existence of histone-like interactions involving the other TAFs is still ambiguous. Here we report the analyses with a two-hybrid system of the mutually interacting regions between hTAF1180 and hTAF1122, which resemble histone H4 and H2B, respectively. The results demonstrate the indispensability of the histone fold motifs of these two TAFs for mutual interaction. Together with earlier biochemical or structural studies, the present results suggest the presence of a histone octamer-like partial TAF complex and its involvement in transcription from chromatin templates. [ABSTRACT FROM AUTHOR]

The homodimeric form of creatine amidinohydrolase from Actinobacillus has been crystallized by the hanging-drop vapour-diffusion method followed by macroseeding using PEG 6000 as a precipitant. The crystals belong to space group I222, with unit-cell parameters a = 111.26 (3), b = 113.62 (4), c = 191.65 (2) Å, and contain two molecules in an asymmetric unit. A complete diffraction data set using synchrotron radiation was collected to 2.7 Å resolution. [ABSTRACT FROM AUTHOR]

Summary: Gankyrin is an oncoprotein commonly overexpressed in most hepatocellular carcinomas. Gankyrin interacts with S6 ATPase of the 19S regulatory particle of the 26S proteasome and enhances the degradation of the tumor suppressors pRb and p53. Here, we report the structure of gankyrin in complex with the C-terminal domain of S6 ATPase. Almost all of the seven ankyrin repeats of gankyrin interact, through its concave region, with the C-terminal domain of S6 ATPase. The intermolecular interactions occur through the complementary charged residues between gankyrin and S6 ATPase. Biochemical studies based on the structure of the complex revealed that gankyrin interacts with pRb in both the presence and absence of S6 ATPase; however, the E182 residue in gankyrin is essential for the pRb interaction. These results provide a structural basis for the involvement of gankyrin in the pRb degradation pathway, through its association with S6 ATPase of the 26S proteasome. [Copyright &y& Elsevier]

Transcription is regulated by a network of transcription factors and related cofactors that act in concert with the general transcription machinery. Elucidating their underlying interactions is important for understanding the mechanisms regulating transcription. Recently, we have shown that Krüppel-like factor KLF5, a member of the Sp/KLF family of zinc finger factors and a key regulator of cardiovascular remodeling, is regulated positively by the acetylase p300 and negatively by the oncogenic regulator SET through coupled interaction and regulation of acetylation. Here, we have shown that the deacetylase HDAC1 can negatively regulate KLF5 through direct interaction. KLF5 interacts with HDAC1 in the cell and in vitro. Gel shift DNA binding assay showed that their interaction inhibits the DNA binding activity of KLFS, suggesting a property of HDAC1 to directly affect the DNA binding affinity of a transcription factor. Reporter assay also revealed that HDAC1 suppresses KLF5-dependent promoter activation. Additionally, overexpression of HDAC1 suppressed KLF5-dependent activation of its endogenous downstream gene, platelet-derived growth factor-A chain gene, when activated by phorbal ester. Further, HDAC1 binds to the first zinc finger of KLF5, which is the same region where p300 interacts with KLF5 and, intriguingly, HDAC1 inhibits binding of p300 to KLF5. Direct competitive interaction between acetylase and deacetylase has been hitherto unknown. Collectively, the transcription factor KLF5 is negatively regulated by the deacetylase HDAC1 through direct effects on its activities (DNA binding activity, promoter activation) and further through inhibition of interaction with p300. These findings suggest a novel role and mechanism for regulation of transcription by deacetylase. [ABSTRACT FROM AUTHOR]