eLife

The functions of the TAF subunits of mammalian TFIID in physiological processes remain poorly characterised. In this study, we describe a novel function of TAFs in directing genomic occupancy of a transcriptional activator. Using liver-specific inactivation in mice, we show that the TAF4 subunit of TFIID is required for post-natal hepatocyte maturation. TAF4 promotes pre-initiation complex (PIC) formation at post-natal expressed liver function genes and down-regulates a subset of embryonic expressed genes by increased RNA polymerase II pausing. The TAF4-TAF12 heterodimer interacts directly with HNF4A and in vivo TAF4 is necessary to maintain HNF4A-directed embryonic gene expression at post-natal stages and promotes HNF4A occupancy of functional cis-regulatory elements adjacent to the transcription start sites of post-natal expressed genes. Stable HNF4A occupancy of these regulatory elements requires TAF4-dependent PIC formation highlighting that these are mutually dependent events. Local promoter-proximal HNF4A-TFIID interactions therefore act as instructive signals for post-natal hepatocyte differentiation

Transcription factor MITF and remodeller BRG1 define chromatin organisation at regulatory elements in melanoma cells

Microphthalmia-associated transcription factor (MITF) is the master regulator of the melanocyte lineage. To understand how MITF regulates transcription, we used tandem affinity purification and mass spectrometry to define a comprehensive MITF interactome identifying novel cofactors involved in transcription, DNA replication and repair, and chromatin organisation. We show that MITF interacts with a PBAF chromatin remodelling complex comprising BRG1 and CHD7. BRG1 is essential for melanoma cell proliferation in vitro and for normal melanocyte development in vivo. MITF and SOX10 actively recruit BRG1 to a set of MITF-associated regulatory elements (MAREs) at active enhancers. Combinations of MITF, SOX10, TFAP2A, and YY1 bind between two BRG1-occupied nucleosomes thus defining both a signature of transcription factors essential for the melanocyte lineage and a specific chromatin organisation of the regulatory elements they occupy. BRG1 also regulates the dynamics of MITF genomic occupancy. MITF-BRG1 interplay thus plays an essential role in transcription regulation in melanoma

TBP as a candidate gene for mental retardation in patients with subtelomeric 6q deletions

International audienceMonozygotic twin brothers with a subtelomeric 6q deletion presented with mental retardation, microcephaly, seizures, an enlarged cisterna magna, dimpling at elbows, a high arched palate and a thin upper lip. The same subtelomeric deletion was detected in the mother of the patients, presenting with a milder phenotype. We narrowed down the breakpoint to a region of approximately 100 kb and estimated the size of the terminal deletion to be 1.2 Mb. This region contains four known and seven putative genes. Comparison of the deletion with other reported patients showed TBP was the most plausible candidate gene for the mental retardation in this syndrome. We verified that the TBP gene expression was halved in our patients using real-time PCR. Cognitive and behavioural tests performed on previously described heterozygous tbp mice suggested that TBP is potentially involved in cognitive development