Biology subjects

Bernardini, A.

Publications and source records attributed to Bernardini, A..

6 recordsLinked to original sources

bioRxiv2026

Cooperative reading of DECA-CCAAT composite element by the TALE/NF-Y/Sp2 transcription factors

To understand how genes are regulated it is important to assess the molecular basis of TFs cooperation in promoter and enhancer regulatory elements. Compelling genetic, genomic and biochemical data in mammals and zebrafish point at DECA-CCAAT composite elements as important for regulation of gene expression in development. DECA is recognized by the homeodomain (HD) heterodimeric TALE TFs (PBX/PREP), CCAAT by the NF-Y trimer. Both are evolutionarily conserved in eukaryotes, including plants. Sp2, a member of the Sp/KLF family, potentiates association of TALE and NF-Y on DNA. We applied AlphaFold to infer the structural basis of the hexameric complex with DNA. The resulting models position TALE and NF-Y on the respective sites, predicting the complex arrangement of the MEINOX/PBC heterodimerization module of the TALE TFs and the sequence-specific DNA contacts of the HDs to DECA. The complex is tied by the Sp2 N-terminus, which contacts the TALE dimer through the -helical SP-box and the NF-Y trimer through a novel short linear motif (YA-SLiM). A flexible linker separates the anchor points, consistent with the constrained stereo-alignment of the DECA-CCAAT motif. The models are confirmed by assembly of the recombinant NF-Y/TALE/Sp2 in complex with DNA in vitro. Mutagenesis confirms the importance of the SP-box and YA-SLiM for cooperativity. Rationalising available genomic and biochemical data, the structural models depict a novel mode of cooperative binding on DNA, providing important clues as to how TFs potentially function beyond DECA-CCAAT in different eukaryotic contexts.

molecular biology↗

bioRxiv2026

A recently evolved TAF8 isoform arising from an Alu insertion increases TFIID assembly complexity in the human lineage

Despite its centrality in regulating RNA polymerase II transcription in all eukaryotes, the TFIID general transcription factor exhibits several layers of variability across different tissues and developmental stages, representing an underexplored hub of evolutionary innovation. Here, we describe a novel short isoform of TAF8 (TAF8s) - a TFIID scaffold subunit - which evolved from the use of an intronic polyadenylation site (iPAS) in the human lineage. Comparative genomics analyses show that the emergence of TAF8s expression in the human lineage coincides with minute DNA changes in the iPAS at the edge of a FLAM-C Alu element that inserted into intron 5 in the common ancestor of anthropoid primates (Simiiformes). The human-specific TAF8s isoform lacks nearly half of the canonical coding sequence, is widely expressed across human tissues, and constitutes a substantial fraction of the TAF8 transcript pool. TAF8s is translated into a truncated protein isoform that lacks the nuclear-localization signal and localises in the cytoplasm. TAF8s interacts with its histone-fold partner TAF10 and other core TFIID subunits, while entirely losing its interactions with TAF2, thus giving rise to alternative TFIID sub-complexes in human cells. Our study suggests that the TFIID complex underwent a recent diversification through a stepwise evolutionary acquisition of complexity in the TAF8 locus in the human lineage, leading to the expression of a novel truncated pan-isoform that might work as a modulator of TFIID assembly. We discuss the ramifications of our findings in TFIID complex diversification, its evolvability, and the genetics of TAF-related congenital disorders.

molecular biology↗

bioRxiv2023

ATAC and SAGA coactivator complexes utilize co-translational assembly, but their cellular localization properties and functions are distinct

To understand the function of multisubunit complexes it is of key importance to uncover the precise mechanisms that guide their assembly. Nascent proteins can find and bind their interaction partners during their translation, leading to co-translational assembly. Here we demonstrate that the core modules of ATAC (ADA-Two-A-Containing) and SAGA (Spt-Ada-Gcn5-acetyltransferase), two lysine acetyl transferase-containing transcription coactivator complexes, assemble co-translationally in the cytoplasm of mammalian cells. In addition, SAGA complex containing all of its modules forms in the cytoplasm and acetylates non-histones proteins. In contrast, fully assembled ATAC complex cannot be detected in the cytoplasm of mammalian cells. However, endogenous ATAC complex containing two functional modules forms and functions in the nucleus. Thus, the two related coactivators, ATAC and SAGA, assemble by using co-translational pathways, but their subcellular localization, cytoplasmic abundance and functions are distinct.

molecular biology↗

bioRxiv2023

Hierarchical TAF1-dependent co-translational assembly of the basal transcription factor TFIID

Large heteromeric multiprotein complexes play pivotal roles at every step of gene expression in eukaryotic cells. Among them, the 20-subunit basal transcription factor TFIID nucleates RNA polymerase II preinitiation complex at gene promoters. Here, by combining systematic RNA-immunoprecipitation (RIP) experiments, single-molecule imaging, proteomics and structure-function analyses, we show that TFIID biogenesis occurs co-translationally. We discovered that all protein heterodimerization steps happen during protein synthesis. We identify TAF1 - the largest protein in the complex - as a critical factor for TFIID assembly. TAF1 acts as a flexible scaffold that drives the co-translational recruitment of TFIID submodules preassembled in the cytoplasm. Altogether, our data suggest a multistep hierarchical model for TFIID biogenesis that culminates with the co-translational assembly of the complex onto the nascent TAF1 polypeptide. We envision that this assembly strategy could be shared with other large heteromeric protein complexes.

molecular biology↗

bioRxiv2019

The inactivation of enzymes belonging to the central carbon metabolism, a novel mechanism of developing antibiotic resistance

Fosfomycin is a bactericidal antibiotic, analogous to phosphoenolpyruvate (PEP) that exerts its activity by inhibiting the activity of MurA. This enzyme catalyzes the first step of peptidoglycan biosynthesis, the transfer of enolpyruvate from PEP to uridine-diphosphate-N-acetylglucosamine. Fosfomycin is increasingly used in the last years, mainly for treating infections caused by Gram-negative multidrug resistant bacteria as Stenotrophomonas maltophilia, an opportunistic pathogen characterized by its low susceptibility to antibiotics of common use. The mechanisms of mutational resistance to fosfomycin in S. maltophilia were studied in the current work. None of the mechanisms so far described for other organisms, which include the production of fosfomycin inactivating enzymes, target modification, induction of alternative peptidoglycan biosynthesis pathway and the impaired entrance of the antibiotic, are involved in the acquisition of such resistance by this bacterial species. Rather the unique cause of resistance in the studied mutants is the mutational inactivation of different enzymes belonging to the Embden-Meyerhof-Parnas central metabolism pathway. The amount of intracellular fosfomycin accumulation did not change in any of these mutants showing that neither the inactivation nor the transport of the antibiotic were involved. Transcriptomic analysis also showed that the mutants did not present changes in the expression level of putative alternative peptidoglycan biosynthesis pathway genes neither any related enzyme. Finally, the mutants did not present an increased PEP concentration that might compete with fosfomycin for its binding to MurA. Based on these results, we describe a completely novel mechanism of antibiotic resistance based on the remodeling of S. maltophilia metabolism.\n\nSignificanceAntibiotic resistance (AR) has been largely considered as a specific bacterial response to an antibiotic challenge. Indeed, its study has been mainly concentrated in mechanisms that affect the antibiotics (mutations in transporters, the activity of efflux pumps and antibiotic modifying enzymes) or their targets (i.e.: target mutations, protection or bypass). Usually, AR-associated metabolic changes were considered to be a consequence (fitness costs) and not a cause of AR. Herein, we show that strong alterations in the bacterial metabolism can also be the cause of AR. In the study here presented, Stenotrophomonas maltophilia acquires fosfomycin resistance through the inactivation of glycolytic enzymes belonging to the Embden-Meyerhof-Parnas. Besides resistance to fosfomycin, this inactivation also impairs the bacterial gluconeogenic pathway. Together with previous work showing that AR can be under metabolic control, our results provide evidence that AR is intertwined with the bacterial metabolism.

microbiology↗

bioRxiv2019

Detection of novel allelic variations in soybean mutant population using Tilling by Sequencing

One of the most important tools in genetic improvement is mutagenesis, which is a useful tool to induce genetic and phenotypic variation for trait improvement and discovery of novel genes. JTN-5203 (MG V) mutant population was generated using an induced ethyl methane sulfonate (EMS) mutagenesis and was used for detection of induced mutations in FAD2-1A and FAD2-1B genes using reverse genetics approach. Optimum concentration of EMS was used to treat 15,000 bulk JTN-5203 seeds producing 1,820 M2 population. DNA was extracted, normalized, and pooled from these individuals. Specific primers were designed from FAD2-1A and FAD2-1B genes that are involved in the fatty acid biosynthesis pathway for further analysis using next-generation sequencing. High throughput mutation discovery through TILLING-by-Sequencing approach was used to detect novel allelic variations in this population. Several mutations and allelic variations with high impacts were detected for FAD2-1A and FAD2-1B. This includes GC to AT transition mutations in FAD2-1A (20%) and FAD2-1B (69%). Mutation density for this population is estimated to be about 1/136kb. Through mutagenesis and high-throughput sequencing technologies, novel alleles underlying the mutations observed in mutants with reduced polyunsaturated fatty acids will be identified, and these mutants can be further used in breeding soybean lines with improved fatty acid profile, thereby developing heart-healthy-soybeans.

plant biology↗