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PQBP-1 was isolated on the basis of its interaction with polyglutamine tracts. In this study, using in vitro and in vivo assays, we show that the association between ataxin-1 and PQBP-1 is positively influenced by expanded polyglutamine sequences. In cell lines, interaction between the two molecules induces apoptotic cell death. As a possible mechanism underlying this phenomenon, we found that mutant ataxin-1 enhances binding of PQBP-1 to the C-terminal domain of RNA polymerase II large subunit (Pol II). This reduces the level of phosphorylated Pol II and transcription. Our results suggest the involvement of PQBP-1 in the pathology of spinocerebellar ataxia type 1 (SCA1) and support the idea that modified transcription underlies polyglutamine-mediated pathology.

Alzheimer’s disease (AD) is the most common neurodegenerative disease, but it remains an intractable condition. Its pathogenesis is predominantly attributed to the aggregation and transmission of two molecules, Aβ and tau; however, other pathological mechanisms are possible. Here, we reveal that phosphorylation of MARCKS, a submembrane protein that regulates the stability of the actin network, occurs at Ser46 prior to aggregation of Aβ and is sustained throughout the course of AD in human and mouse brains. Furthermore, HMGB1 released from necrotic or hyperexcitatory neurons binds to TLR4, triggers the specific phosphorylation of MARCKS via MAP kinases, and induces neurite degeneration, the classical hallmark of AD pathology. Subcutaneous injection of a newly developed monoclonal antibody against HMGB1 strongly inhibits neurite degeneration even in the presence of Aβ plaques and completely recovers cognitive impairment in a mouse model. HMGB1 and Aβ mutually affect polymerization of the other molecule, and the therapeutic effects of the anti-HMGB1 monoclonal antibody are mediated by Aβ-dependent and Aβ-independent mechanisms. We propose that HMGB1 is a critical pathogenic molecule promoting AD pathology in parallel with Aβ and tau and a new key molecular target of preclinical antibody therapy to delay the onset of AD.

Oct3 is an embryonic octamer‐binding transcription factor, whose expression is rapidly repressed by retinoic acid (RA). In this report, we have determined the transcriptional control region of the oct3 gene and studied the mechanism of the RA‐mediated repression. The chromosomal oct3 gene consists of five exons. Three subdomains of the POU region and transactivating domain are located in separate exons. Transcription initiates at multiple sites in the GC‐rich region lacking a typical TATA box. The upstream 2 kb region can confer the cell type‐specific expression and RA‐mediated repression. Analysis of the upstream region by deletion mutagenesis locates a cis element (RARE1) which functions as a stem cell‐specific, yet RA‐repressible, enhancer. Footprint and gel‐retardation assays show that RARE1 is composed of two domains, each of which is recognized by distinct factors. Microinjection of oct3‐lacZ constructs into fertilized eggs indicates that RARE1 can function in early embryos. We suggest that RARE1 is a critical cis element for oct3 gene expression in embryonic stem cells and for the RA‐mediated repression.