ABSTRACT
Frontotemporal lobar degeneration (FTLD) causes frontotemporal dementia (FTD), the most common form of dementia after Alzheimer's disease, and is often also associated with motor disorders1. The pathological hallmarks of FTLD are neuronal inclusions of specific, abnormally assembled proteins2. In the majority of cases the inclusions contain amyloid filament assemblies of TAR DNA-binding protein 43 (TDP-43) or tau, with distinct filament structures characterizing different FTLD subtypes3,4. The presence of amyloid filaments and their identities and structures in the remaining approximately 10% of FTLD cases are unknown but are widely believed to be composed of the protein fused in sarcoma (FUS, also known as translocated in liposarcoma). As such, these cases are commonly referred to as FTLD-FUS. Here we used cryogenic electron microscopy (cryo-EM) to determine the structures of amyloid filaments extracted from the prefrontal and temporal cortices of four individuals with FTLD-FUS. Surprisingly, we found abundant amyloid filaments of the FUS homologue TATA-binding protein-associated factor 15 (TAF15, also known as TATA-binding protein-associated factor 2N) rather than of FUS itself. The filament fold is formed from residues 7-99 in the low-complexity domain (LCD) of TAF15 and was identical between individuals. Furthermore, we found TAF15 filaments with the same fold in the motor cortex and brainstem of two of the individuals, both showing upper and lower motor neuron pathology. The formation of TAF15 amyloid filaments with a characteristic fold in FTLD establishes TAF15 proteinopathy in neurodegenerative disease. The structure of TAF15 amyloid filaments provides a basis for the development of model systems of neurodegenerative disease, as well as for the design of diagnostic and therapeutic tools targeting TAF15 proteinopathy.
Subject(s)
Frontotemporal Lobar Degeneration , TATA-Binding Protein Associated Factors , Humans , Amyloid/chemistry , Amyloid/metabolism , Amyloid/ultrastructure , Brain Stem/metabolism , Brain Stem/pathology , Cryoelectron Microscopy , Frontotemporal Dementia/etiology , Frontotemporal Dementia/metabolism , Frontotemporal Dementia/pathology , Frontotemporal Lobar Degeneration/complications , Frontotemporal Lobar Degeneration/metabolism , Frontotemporal Lobar Degeneration/pathology , Motor Cortex/metabolism , Motor Cortex/pathology , Motor Neurons/metabolism , Motor Neurons/pathology , Prefrontal Cortex/metabolism , Prefrontal Cortex/pathology , TATA-Binding Protein Associated Factors/chemistry , TATA-Binding Protein Associated Factors/metabolism , TATA-Binding Protein Associated Factors/ultrastructure , Temporal Lobe/metabolism , Temporal Lobe/pathologyABSTRACT
The general transcription factor IID (TFIID) plays a central role in the initiation of RNA polymerase II (Pol II)-dependent transcription by nucleating pre-initiation complex (PIC) assembly at the core promoter. TFIID comprises the TATA-binding protein (TBP) and 13 TBP-associated factors (TAF1-13), which specifically interact with a variety of core promoter DNA sequences. Here we present the structure of human TFIID in complex with TFIIA and core promoter DNA, determined by single-particle cryo-electron microscopy at sub-nanometre resolution. All core promoter elements are contacted by subunits of TFIID, with TAF1 and TAF2 mediating major interactions with the downstream promoter. TFIIA bridges the TBP-TATA complex with lobe B of TFIID. We also present the cryo-electron microscopy reconstruction of a fully assembled human TAF-less PIC. Superposition of common elements between the two structures provides novel insights into the general role of TFIID in promoter recognition, PIC assembly, and transcription initiation.
Subject(s)
Promoter Regions, Genetic/genetics , Transcription Factor TFIID/metabolism , Transcription Factor TFIID/ultrastructure , Transcription Initiation, Genetic , Cryoelectron Microscopy , DNA/chemistry , DNA/metabolism , DNA/ultrastructure , Humans , Models, Molecular , Protein Binding , Substrate Specificity , TATA Box/genetics , TATA-Binding Protein Associated Factors/chemistry , TATA-Binding Protein Associated Factors/metabolism , TATA-Binding Protein Associated Factors/ultrastructure , TATA-Box Binding Protein/chemistry , TATA-Box Binding Protein/metabolism , TATA-Box Binding Protein/ultrastructure , Transcription Factor TFIIA/chemistry , Transcription Factor TFIIA/metabolism , Transcription Factor TFIIA/ultrastructure , Transcription Factor TFIID/chemistryABSTRACT
Proper ovarian development requires the cell type-specific transcription factor TAF4b, a subunit of the core promoter recognition complex TFIID. We present the 35 A structure of a cell type-specific core promoter recognition complex containing TAF4b and TAF4 (4b/4-IID), which is responsible for directing transcriptional synergy between c-Jun and Sp1 at a TAF4b target promoter. As a first step toward correlating potential structure/function relationships of the prototypic TFIID versus 4b/4-IID, we have compared their 3D structures by electron microscopy and single-particle reconstruction. These studies reveal that TAF4b incorporation into TFIID induces an open conformation at the lobe involved in TFIIA and putative activator interactions. Importantly, this open conformation correlates with differential activator-dependent transcription and promoter recognition by 4b/4-IID. By combining functional and structural analysis, we find that distinct localized structural changes in a megadalton macromolecular assembly can significantly alter its activity and lead to a TAF4b-induced reprogramming of promoter specificity.
