Project description:Determining structures of protein complexes is crucial for understanding cellular functions. Here, we describe an integrative structure determination approach that relies on in vivo measurements of genetic interactions. We construct phenotypic profiles for point mutations crossed against gene deletions or exposed to environmental perturbations, followed by converting similarities between two profiles into an upper bound on the distance between the mutated residues. We determine the structure of the yeast histone H3/4 complex based on ~500,000 genetic interactions of 350 mutants. We then apply the method to subunits Rpb1-Rpb2 of yeast RNA polymerase II, and subunits RpoB-RpoC of bacterial RNA polymerase. The accuracy is comparable to that based on chemical cross-links; using restraints from both genetic interactions and cross-links further improves model accuracy and precision. The approach provides an efficient means to augment integrative structure determination with in vivo observations.
Project description:To identify the cuticular proteins in developing wing scales of Bombyx mori, we performed LC-MS/MS analysis of dissoliving developing wing scales from Bombyx mori
Project description:To identify the cuticular proteins in developing wing scales of Bombyx mori, we performed LC-MS/MS analysis of dissoliving developing wing scales from Bombyx mori
Project description:To identify the cuticular proteins in developing wing scales of Bombyx mori, we performed LC-MS/MS analysis of dissoliving developing wing scales from Bombyx mori
Project description:Birds and other reptiles possess a diversity of feather and scale-like skin appendages. Feathers are commonly assumed to have originated from ancestral scales in theropod dinosaurs. However, most birds also have scaled feet, indicating birds evolved the capacity to grow both ancestral and derived morphologies. This suggests a more complex evolutionary history than a simple linear transition between feathers and scales. We set out to investigate the evolution of feathers via the comparison of transcriptomes assembled from diverse skin appendages in chicken, emu, and alligator. Our data reveal that feathers and the overlapping ‘scutate’ scales of birds share more similar gene expression to each other, and to two types of alligator scales, than they do to the tuberculate ‘reticulate’ scales on bird footpads. Accordingly, we propose a history of skin appendage diversification, in which feathers and bird scutate scales arose from ancestral archosaur body scales, whereas reticulate scales arose earlier in tetrapod evolution. We also show that many “feather-specific genes” are also expressed in alligator scales. In-situ hybridization results in feather buds suggest that these genes represent ancestral scale genes that acquired novel roles in feather morphogenesis and were repressed in bird scales. Our findings suggest that the differential reuse, in feathers, and suppression, in bird scales, of genes ancestrally expressed in archosaur scales has been a key factor in the origin of feathers – and may represent an important mechanism for the origin of evolutionary novelties.
Project description:Epidermal keratinocytes form cornified skin appendages such as scutate scales on the legs of birds. Here, we investigated the molecular pathways of keratinocyte differentiation in chicken scutate scales by single cell transcriptomics. We identified two distinct populations of differentiated keratinocytes. The first type of differentiated keratinocytes is characterized by mRNAs encoding scale-type corneous beta-proteins (CBPs), also known as beta-keratins and cysteine-rich keratins, indicating that these cells form hard scales. The second type of differentiated keratinocytes contains mRNAs encoding keratinocyte-type CBPs and cysteine-poor keratins, indicating that these cells form the soft interscale epidermis. Immunostaining with a newly raised antibody confirmed that keratin 9-like cysteine-rich 2 (KRT9LC2) or Hard Acid Sauropsid-specific 2 (HAS2) keratin, which is a marker of the first type of keratinocytes, is expressed in the suprabasal epidermal layers of scutate scales but not in interscale epidermis. Furthermore, mRNA of CTNN1B, previously implicated in scale placode formation, was enriched in differentiated scale keratinocytes, whereas genes involved in lipid metabolism, such as ELOVL4 and FADS1 were enriched in keratinocytes of the interscale epidermis. In conclusion, this study defines the gene expression programs that build the scutate scales and interscale epidermis of birds.
Project description:In vivo protein-DNA interactions connect each transcription factor with its direct targets to form a gene network scaffold. To map these protein-DNA interactions comprehensively across entire mammalian genomes, we developed a large-scale chromatin immunoprecipitation assay (ChIPSeq) based on direct ultrahigh-throughput DNA sequencing. This sequence census method was then used to map in vivo binding of the neuron-restrictive silencer factor (NRSF; also known as REST, for repressor element–1 silencing transcription factor) to 1946 locations in the human genome. The data display sharp resolution of binding position [±50 base pairs (bp)], which facilitated our finding motifs and allowed us to identify noncanonical NRSF-binding motifs. These ChIPSeq data also have high sensitivity and specificity [ROC (receiver operator characteristic) area ≥ 0.96] and statistical confidence (P < 10−4), properties that were important for inferring new candidate interactions. These include key transcription factors in the gene network that regulates pancreatic islet cell development.
Project description:Delineating how chromosomes fold at length scales beyond one megabase remains obscure relative to smaller-scale folding into TADs, loops, and nucleosomes. We find that rather than simply unfolding chromatin, histone hyperacetylation results in interactions between distant genomic loci separated by tens to hundreds of megabases, even in the absence of transcription. These hyperacetylated “megadomains” are formed by the BRD4-NUT fusion oncoprotein, interact both within and between chromosomes, and form a specific nuclear subcompartment that has elevated gene activity with respect to other subcompartments. Pharmacological degradation of BRD4-NUT results in collapse of megadomains and attenuation of the interactions between them. In contrast, these interactions persist and contacts between newly acetylated regions are formed after inhibiting RNA polymerase II initiation. Our structure-function approach thus reveals that broad chromatin domains of identical biochemical composition, independent of transcription, form nuclear subcompartments, and also indicates the potential of altering chromosome structure for treating human disease.