POZ Domain Transcription Factor, FBI-1, Represses Transcription of ADH5/FDH by Interacting with the Zinc Finger and Interfering with DNA Binding Activity of Sp1

Abstract

The POZ domain is a protein-protein interaction motif that is found in many transcription factors, which are important for development, oncogenesis, apoptosis, and transcription repression. We cloned the POZ domain transcription factor, FBI-1, that recognizes the cis-element (bp ؊38 to ؊22) located just upstream of the core Sp1 binding sites (bp ؊22 to ؉22) of the ADH5/FDH minimal promoter (bp ؊38 to ؉61) in vitro and in vivo, as revealed by electrophoretic mobility shift assay and chromatin immunoprecipitation assay. The ADH5/FDH minimal promoter is potently repressed by the FBI-1. Glutathione S-transferase fusion protein pull-down showed that the POZ domains of FBI-1, Plzf, and Bcl-6 directly interact with the zinc finger DNA binding domain of Sp1. DNase I footprinting assays showed that the interaction prevents binding of Sp1 to the GC boxes of the ADH5/FDH promoter. Gal4-POZ domain fusions targeted proximal to the GC boxes repress transcription of the Gal4 upstream activator sequence-Sp1-adenovirus major late promoter. Our data suggest that POZ domain represses transcription by interacting with Sp1 zinc fingers and by interfering with the DNA binding activity of Sp1.

Transcriptional Activity of Sp1 Is Regulated by Molecular Interactions between the Zinc Finger DNA Binding Domain and the Inhibitory Domain with Corepressors, and This Interaction Is Modulated by MEK

“…), and these interactions have proved to be crucial in the regulation of many cellular functions by transcription-level control of gene expression. We, along with other investigators (9,21,22), determined that the most highly conserved region of Sp1, the Sp1ZFDBD, is involved in proteinprotein interactions with other proteins, including the POZ domains of FBI-1, p300, and HDAC1.…”

“…To activate transcription, Sp1 also interacts with nuclear proteins such as the TATA-box-binding protein TBP, and the TBPassociated factors dTAFII130, hTAFII130, hTAFII55, and CRSP (a cofactor required for Sp1 activation). Sp1 also interacts with a variety of other transcription factors, such as the retinoblastoma-related proteins p107, YY1, E2F, HDAC1, p300, and FBI-1 (9,(15)(16)(17)(18)(19)(20)(21)(22). Currently, available data suggest that Sp1 acts mainly as a transcription activator, but also, in some cases, as a transcription repressor (Refs.…”

“…porter System-Previous reports revealed that Sp1ZFDBD interacts with the HDAC1 and POZ domains (21,22). It was suspected that the Sp1ZFDBD and the Sp1ID might also interact with the other polypeptides involved in transcription repression, and that these interactions may be important in the regulation of Sp1 activity.…”

Role of LRF/Pokemon in lineage fate decisions

“…Recently, however, the inventory of LRF/Pokemon interactors has been expanded to include other transcription factors such as tumor protein p53 (TP53), androgen receptor, specificity protein 1, BCL6, sex determining region Y-box 9 (SOX9), and growth factor independent 1, thereby suggesting an indirect transcriptional repressive activity of LRF on specific subclasses of genes ( Figure 1B). [10][11][12][13][14][15][16][17][18] These findings in turn highlight LRF as a key node for the transcriptional regulation of fundamental pathways involved in cell cycle control, apoptosis, and cell fate decision.…”

“…Finally, the poorly conserved hinge region between the POZ and ZF domains, as well as the C terminus at the end of the ZFs domains, are often the targets of posttranslational modifications responsible for the regulation of protein function ( Figure 1A). [10][11][12][13][14][15][16][17][18] Multiple POK proteins, LRF included, have been shown to act as transcriptional repressors by directly binding specific consensus sequences on DNA and interacting with corepressors such as NCoR, SMRT, and Sin3a via the POZ domain at the N terminus. 19,20 For its part, LRF preferentially binds to the GC-rich sequence [(G/A)(C/A)GACCCC], as has been revealed by cyclic amplification and selection of target analysis, 21 gelshift assay, 22 and chromatin immunoprecipitation sequencing.…”