The TATA-box binding protein-associated factor TAF12b facilitates the degradation of type-B response regulators to negatively regulate cytokinin signaling.

Cytokinins (CKs) are one of important classes of plant hormones essential for plant growth and development. The TATA-box binding protein-associated factor 12b (TAF12b) is involved in cytokinin (CK) signaling, but its molecular and biochemical mechanisms remain unclear. In this study, TAF12b of Nicotiana benthamiana (NbTAF12b) was found to mediate CK response by directly interacting with type-B response regulators (B-RRs), which are positive regulators of CK signaling, and inhibiting their transcriptional activities. The co-factor specifically facilitated the proteasomal degradation of non-phosphorylated B-RRs by recruiting the KMD family of F-box proteins. Such interactions between TAF12b and B-RRs also occur in other plant species. Genetic transformation experiments further showed that overexpression of NbTAF12b attenuates the CK-hypersensitive phenotype conferred by NbRR1 overexpression. Taken together, these results suggest a conserved mechanism that TAF12b negatively regulates CK responses through promoting 26S proteasome-mediated degradation of B-RRs degradation in multiple plant species, which provides novel insights into the regulatory network of CK signaling in plants.

TATA-binding associated factors have distinct roles during early mammalian development.

Early embryonic development is a finely orchestrated process that requires precise regulation of gene expression coordinated with morphogenetic events. TATA-box binding protein-associated factors (TAFs), integral components of transcription initiation coactivators like TFIID and SAGA, play a crucial role in this intricate process. Here we show that disruptions in TAF5, TAF12 and TAF13 individually lead to embryonic lethality in the mouse, resulting in overlapping yet distinct phenotypes. Taf5 and Taf12 mutant embryos exhibited a failure to implant post-blastocyst formation, and Taf5 mutants have aberrant lineage specification within the inner cell mass. In contrast, Taf13 mutant embryos successfully implant and form egg-cylinder stages but fail to initiate gastrulation. Strikingly, we observed a depletion of pluripotency factors in TAF13-deficient embryos, including OCT4, NANOG and SOX2, highlighting an indispensable role of TAF13 in maintaining pluripotency. Transcriptomic analysis revealed distinct gene targets affected by the loss of TAF5, TAF12 and TAF13. Thus, we propose that TAF5, TAF12 and TAF13 convey locus specificity to the TFIID complex throughout the mouse genome.

Deciphering Selectivity Mechanism of BRD9 and TAF1(2) toward Inhibitors Based on Multiple Short Molecular Dynamics Simulations and MM-GBSA Calculations.

BRD9 and TAF1(2) have been regarded as significant targets of drug design for clinically treating acute myeloid leukemia, malignancies, and inflammatory diseases. In this study, multiple short molecular dynamics simulations combined with the molecular mechanics generalized Born surface area method were employed to investigate the binding selectivity of three ligands, 67B, 67C, and 69G, to BRD9/TAF1(2) with IC50 values of 230/59 nM, 1400/46 nM, and 160/410 nM, respectively. The computed binding free energies from the MM-GBSA method displayed good correlations with that provided by the experimental data. The results indicate that the enthalpic contributions played a critical factor in the selectivity recognition of inhibitors toward BRD9 and TAF1(2), indicating that 67B and 67C could more favorably bind to TAF1(2) than BRD9, while 69G had better selectivity toward BRD9 over TAF1(2). In addition, the residue-based free energy decomposition approach was adopted to calculate the inhibitor-residue interaction spectrum, and the results determined the gatekeeper (Y106 in BRD9 and Y1589 in TAF1(2)) and lipophilic shelf (G43, F44, and F45 in BRD9 and W1526, P1527, and F1528 in TAF1(2)), which could be identified as hotspots for designing efficient selective inhibitors toward BRD9 and TAF1(2). This work is also expected to provide significant theoretical guidance and insightful molecular mechanisms for the rational designs of efficient selective inhibitors targeting BRD9 and TAF1(2).

Elevated TAF12 Expression Predicts Poor Prognosis in Glioma Patients: Evidence from Bioinformatic and Immunohistochemical Analyses.

TATA box-binding protein-associated factor 12 (TAF12) has been identified as an oncogene in choroid plexus carcinoma, but its role in glioma is poorly understood because of a lack of previous studies. This study investigated the relationship of TAF12 expression with the clinicopathologic features of glioma cases, as well as its prognostic value and biological function, using large-scale databases and clinical samples. TAF12 mRNA expression and clinicopathologic characteristics of glioma cases were assessed in three public databases, and bioinformatics analyses were conducted to explore the prognostic value and biological functions of TAF12 in glioma. High TAF12 expression was commonly associated with reduced survival time and poor clinical indexes, including higher World Health Organization grade, wild-type isocitrate dehydrogenase 1 expression, and 1p19q non-codeletion status (p < 0.0001). Multivariate Cox regression analysis showed that high TAF12 expression was an independent poor prognostic factor for glioma patients (hazard ratio = 1.41, 95% confidence interval, 1.18-1.68, p < 0.001). Functional enrichment analysis revealed involvement of TAF12 in immune and inflammatory responses in glioma. Also, expression of several immune checkpoint molecules was significantly higher in samples with high TAF12 expression. TAF12 is a potential independent prognostic factor for glioma, and these findings provide a foundation for further investigation of the potential role of TAF12 in immunotherapy.

A TFIID-SAGA Perturbation that Targets MYB and Suppresses Acute Myeloid Leukemia.

Targeting of general coactivators is an emerging strategy to interfere with oncogenic transcription factors (TFs). However, coactivator perturbations often lead to pleiotropic effects by influencing numerous TFs. Here we identify TAF12, a subunit of TFIID and SAGA coactivator complexes, as a selective requirement for acute myeloid leukemia (AML) progression. We trace this dependency to a direct interaction between the TAF12/TAF4 histone-fold heterodimer and the transactivation domain of MYB, a TF with established roles in leukemogenesis. Ectopic expression of the TAF4 histone-fold fragment can efficiently squelch TAF12 in cells, suppress MYB, and regress AML in mice. Our study reveals a strategy for potent MYB inhibition in AML and highlights how an oncogenic TF can be selectively neutralized by targeting a general coactivator complex.

Functional specialization of two paralogous TAF12 variants by their selective association with SAGA and TFIID transcriptional regulatory complexes.

TATA box-binding protein (TBP)-associated factors (TAFs), evolutionarily conserved from yeast to humans, play a central role during transcription initiation. A subset of TAF proteins is shared in transcription factor II D (TFIID) and SAGA transcription regulatory complexes. Although higher eukaryotes contain multiple TAF variants that specify tissue- and developmental stage-specific organization of TFIID or SAGA complexes, in unicellular genomes, however, each TAF is encoded by a single gene. Surprisingly, we found that the genome of Candida albicans, the predominant human fungal pathogen, contains two paralogous TAF12 genes, CaTAF12L and CaTAF12, encoding H2B-like histone-fold domain-containing variants. Of the available fungal genome sequences, only seven other closely related diploid pathogenic Candida genomes encode the two TAF12 paralogs. Using affinity purifications from C. albicans cell extracts, we demonstrate that CaTAF12L uniquely associates with the SAGA complex and CaTAF12 associates with the TFIID complex. We further show that CaTAF12, but not CaTAF12L, is essential for C. albicans growth. Conditional depletion of the two TAF12 variant proteins caused distinct cellular and colony phenotypes. Together our results define a specialized organization of the TAF12 variants and non-redundant roles for the two TAF12 variants in the unicellular C. albicans genome.