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Homozygous TAF8 mutation in a patient with intellectual disability results in undetectable TAF8 protein, but preserved RNA polymerase II transcription.

ABSTRACT: The human general transcription factor TFIID is composed of the TATA-binding protein (TBP) and 13 TBP-associated factors (TAFs). In eukaryotic cells, TFIID is thought to nucleate RNA polymerase II (Pol II) preinitiation complex formation on all protein coding gene promoters and thus, be crucial for Pol II transcription. In a child with intellectual disability, mild microcephaly, corpus callosum agenesis and poor growth, we identified a homozygous splice-site mutation in TAF8 (NM_138572.2: c.781-1G?>?A). Our data indicate that the patient's mutation generates a frame shift and an unstable TAF8 mutant protein with an unrelated C-terminus. The mutant TAF8 protein could not be detected in extracts from the patient's fibroblasts, indicating a loss of TAF8 function and that the mutation is most likely causative. Moreover, our immunoprecipitation and proteomic analyses show that in patient cells only partial TAF complexes exist and that the formation of the canonical TFIID is impaired. In contrast, loss of TAF8 in mouse embryonic stem cells and blastocysts leads to cell death and to a global decrease in Pol II transcription. Astonishingly however, in human TAF8 patient cells, we could not detect any cellular phenotype, significant changes in genome-wide Pol II occupancy and pre-mRNA transcription. Thus, the disorganization of the essential holo-TFIID complex did not affect global Pol II transcription in the patient's fibroblasts. Our observations further suggest that partial TAF complexes, and/or an altered TFIID containing a mutated TAF8, could support human development and thus, the absence of holo-TFIID is less deleterious for transcription than originally predicted.

SUBMITTER: El-Saafin F

PROVIDER: S-EPMC5985725 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Homozygous TAF8 mutation in a patient with intellectual disability results in undetectable TAF8 protein, but preserved RNA polymerase II transcription.

El-Saafin Farrah F Curry Cynthia C Ye Tao T Garnier Jean-Marie JM Kolb-Cheynel Isabelle I Stierle Matthieu M Downer Natalie L NL Dixon Mathew P MP Negroni Luc L Berger Imre I Thomas Tim T Voss Anne K AK Dobyns William W Devys Didier D Tora Laszlo L

Human molecular genetics 20180601 12

The human general transcription factor TFIID is composed of the TATA-binding protein (TBP) and 13 TBP-associated factors (TAFs). In eukaryotic cells, TFIID is thought to nucleate RNA polymerase II (Pol II) preinitiation complex formation on all protein coding gene promoters and thus, be crucial for Pol II transcription. In a child with intellectual disability, mild microcephaly, corpus callosum agenesis and poor growth, we identified a homozygous splice-site mutation in TAF8 (NM_138572.2: c.781- ...[more]

PMID: 29648665

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Project description:The Wiskott-Aldrich Syndrome Protein (WASP) family is known for its participation in cytoskeleton reorganization (Marchand et al., 2001 and Jia et al., 2010). In 2007, the human subtelomeric MGC52000 genes were renamed as Wiskott-Aldrich Syndrome Protein and SCAR Homolog (WASH). Human WASH proteins are part of the WASP protein family and colocalize with actin in cells and promote Arp2/3-dependent actin polymerization in vitro (Linardopoulou et al., 2007). WASH multiprotein complex consists of seven subunits: notable to mention Strumpelin and Was Protein Family Homolog (WASH)-interacting protein (SWIP), which is encoded by KIAA1033/WASHC4 gene, FAM21 and Arp2/3. The Arp2/3 dependent actin polymerization from G-actin to F-actin is an important step in regulation of the cytoskeleton, enabling multiple endosomal transport processes (Kelleher et al., 1995 and Derivery et al., 2010). Linardopoulou and colleagues have also shown in an animal model (Drosophila), that the single WASH ortholog is essential for viability (Linardopoulou et al., 2007), strengthening the concept, that WASHC4 plays a crucial role in muscle cell integrity and function. A link between autosomal recessive intellectual disability (ARID) and mutations in the KIAA1033/WASHC4 gene was first recognized in 2011 by Ropers and colleagues. Very recently, Assoum and colleagues reported three additional patients (from two unrelated families) with syndromic ID. Two of them being sisters (8 and 6 years), both presenting with learning disabilities, macrocephaly, dysmorphic features, skeletal anomalies and subependymal heterotopic nodules due to a compound heterozygous mutation of the KIAA1033/WASHC4 gene (p.[Gln442*] and p.[Asp1048Gly]). In this study, we precisely describe the clinical phenotype of the two siblings and provide additional information (histological and proteomic data) derived from the muscle biopsy of the elder sibling to confirm the pathogenicity of the reported variant and establish the function of WASHC4 as relevant for muscle homeostasis. Which, as far as the authors know, has not yet been described in literature.

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Homozygous TAF8 mutation in a patient with intellectual disability results in undetectable TAF8 protein, but preserved RNA polymerase II transcription.

Publications

Homozygous TAF8 mutation in a patient with intellectual disability results in undetectable TAF8 protein, but preserved RNA polymerase II transcription.

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