Koidl, S. | bioRxiv Science

bioRxiv2024

TAF2 condensation in nuclear speckles links basal transcription factor TFIID to RNA splicing

TFIID is an essential basal transcription factor, crucial for RNA polymerase II (pol II) promoter recognition and transcription initiation. The TFIID complex consists of the TATA-binding protein (TBP) and 13 TBP-associated factors (TAFs) that contain intrinsically disordered regions (IDRs) with currently unknown functions. Here, we show that a conserved IDR drives TAF2 condensation in nuclear speckles, independently of other TFIID subunits. Quantitative mass spectrometry analyses reveal that the TAF2 IDR specifically interacts with the nuclear speckle and spliceosome-associated protein SRRM2. Consequently, TAF2 recruits SRRM2 to TFIID to form non-canonical TFIID-SRRM2 complexes. Reduced SRRM2 recruitment elicits alternative splicing events in RNAs coding for proteins involved in transcription and transmembrane transport. Further, genome-wide binding analyses suggest TAF2 shuttling between nuclear speckles and pol II promoters. This study identifies an IDR of the basal transcription machinery as a molecular guide for protein partitioning into nuclear compartments, controlling protein complex composition and pre-mRNA splicing.

molecular biology↗

bioRxiv2022

Multi-omics analyses of MEN1 missense mutations identify disruption of menin-MLL and menin-JunD interactions as critical requirements for molecular pathogenicity

Loss-of-function mutations of the multiple endocrine neoplasia type 1 (MEN1) gene are causal to the MEN1 tumor syndrome, but they are also commonly found in sporadic pancreatic neuroendocrine tumors and other types of cancers. The MEN1 gene product, menin, is involved in transcriptional and chromatin regulation, most prominently as an integral component of KMT2A/MLL1 and KMT2B/MLL2 containing COMPASS-like histone H3K4 methyltransferase complexes. In a mutually exclusive fashion, menin also interacts with the JunD subunit of the AP-1 and ATF/CREB transcription factors. After in silico screening of 253 disease-related MEN1 missense mutations, we selected a set of nine menin mutations in surface-exposed residues. The protein interactomes of these mutants were assessed by quantitative mass spectrometry, which indicated that seven of the nine mutants disrupt interactions with both MLL1/2 and JunD complexes. Interestingly, we identified three missense mutations, R52G, E255K and E359K, which predominantly reduce the interaction with MLL1 compared to JunD. This observation was supported by a pronounced loss of binding of the R52G, E255K and E359K mutant proteins at unique MLL1 genomic binding sites with less effect on unique JunD sites. These findings support the general importance of the menin-MLL1 and menin-JunD interactions in MEN1 gene-associated pathogenic conditions.

molecular biology↗