title: Interaction between isolated transcriptional activation domains of Sp1 revealed by heteronuclear magnetic resonance.
abstract: The promoter-specific transcription factor Sp1 is expressed ubiquitously, and plays a primary role in the regulation of the expression of many genes. Domains A and B located in the N-terminal half of the protein are characterized by glutamine-rich (Q-rich) sequences. These Q-rich domains have been shown to be involved in the interaction between Sp1 and different classes of nuclear proteins, such as TATA-binding protein associated factors. Furthermore, the self-association of Sp1 via Q-rich domains is also important for the regulation of transcriptional activity. It has been considered that an Sp1 molecule bound to a "distal" GC-box synergistically interacts with another Sp1 molecule at a "proximal" binding site. Although the formation of multimers via Q-rich domains seems functionally important for Sp1, little is known about the structural and physicochemical nature of the interaction between Q-rich domains. We analyzed the structural details of isolated glutamine-rich B (QB) domains of Sp1 by circular dichroism (CD), analytical ultracentrifugation, and heteronuclear magnetic resonance spectroscopy (NMR). We found the isolated QB domains to be disordered under all conditions examined. Nevertheless, a detailed analysis of NMR spectra clearly indicated interaction between the domains. In particular, the C-terminal half was responsible for the self-association. Furthermore, analytical ultracentrifugation demonstrated weak but significant interaction between isolated QB domains. The self-association between QB domains would be responsible, at least in part, for the formation of multimers by full-length Sp1 molecules that has been proposed to occur during transcriptional activation.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-Shimoadachi, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Hiramatsu
authors.forename: Emi
authors.initials: E
authors.lastname: Hibino
authors.forename: Katsumi
authors.initials: K
authors.lastname: Matsuzaki
authors.forename: Jun
authors.initials: J
authors.lastname: Kuwahara
authors.forename: Masaru
authors.initials: M
authors.lastname: Hoshino
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D005973:Glutamine / Q000737:chemistry; D006801:Humans; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016329:Sp1 Transcription Factor / Q000737:chemistry* / Q000378:metabolism*; D014461:Ultracentrifugation
chemical_list: D016329:Sp1 Transcription Factor; D005973:Glutamine