In this task, you are given an abstract of article. Your task is to generate title for this article. Preferred titles are under thirty words.

Input: Consider Input: Most protein complexes are inaccessible to high resolution structural analysis. We report the results of a combined approach of cross-linking, mass spectrometry, and bioinformatics to two human complexes containing large coiled-coil segments, the NDEL1 homodimer and the NDC80 heterotetramer. An important limitation of the cross-linking approach, so far, was the identification of cross-linked peptides from fragmentation spectra. Our novel approach overcomes the data analysis bottleneck of cross-linking and mass spectrometry. We constructed a purpose-built database to match spectra with cross-linked peptides, define a score that expresses the quality of our identification, and estimate false positive rates. We show that our analysis sheds light on critical structural parameters such as the directionality of the homodimeric coiled coil of NDEL1, the register of the heterodimeric coiled coils of the NDC80 complex, and the organization of a tetramerization region in the NDC80 complex. Our approach is especially useful to address complexes that are difficult in addressing by standard structural methods.

Output: Structural analysis of multiprotein complexes by cross-linking, mass spectrometry, and database searching.

Input: Consider Input: A population of fibro/adipogenic but non-myogenic progenitors located between skeletal muscle fibers was recently discovered. The aim of this study was to determine the extent to which these progenitors differentiate into fully functional adipocytes. The characterization of muscle progenitor-derived adipocytes is a central issue in understanding muscle homeostasis. They are considered as being the cellular origin of intermuscular adipose tissue that develops in several pathophysiological situations. Here fibro/adipogenic progenitors were isolated from a panel of 15 human muscle biopsies on the basis of the specific cell-surface immunophenotype CD15+/PDGFR+CD56-. This allowed investigations of their differentiation into adipocytes and the cellular functions of terminally differentiated adipocytes. Adipogenic differentiation was found to be regulated by the same effectors as those regulating differentiation of progenitors derived from white subcutaneous adipose tissue. Similarly, basic adipocyte functions, such as triglyceride synthesis and lipolysis occurred at levels similar to those observed with subcutaneous adipose tissue progenitor-derived adipocytes. However, muscle progenitor-derived adipocytes were found to be insensitive to insulin-induced glucose uptake, in association with the impairment of phosphorylation of key insulin-signaling effectors. Our findings indicate that muscle adipogenic progenitors give rise to bona fide white adipocytes that have the unexpected feature of being insulin-resistant.

Output: Characterization of adipocytes derived from fibro/adipogenic progenitors resident in human skeletal muscle

Input: Consider Input: Transcriptional regulatory elements play essential roles in gene expression during animal development and cellular response to environmental signals, but our knowledge of these regions in the human genome is limited despite the availability of the complete genome sequence. Promoters mark the start of every transcript and are an important class of regulatory elements. A large, complex protein structure known as the pre-initiation complex (PIC) is assembled on all active promoters, and the presence of these proteins distinguishes promoters from other sequences in the genome. Using components of the PIC as tags, we isolated promoters directly from human cells as protein-DNA complexes and identified the resulting DNA sequences using genomic tiling microarrays. Our experiments in four human cell lines uncovered 252 PIC-binding sites in 44 semirandomly selected human genomic regions comprising 1% (30 megabase pairs) of the human genome. Nearly 72% of the identified fragments overlap or immediately flank 5' ends of known cDNA sequences, while the remainder is found in other genomic regions that likely harbor putative promoters of unannotated transcripts. Indeed, molecular analysis of the RNA isolated from one cell line uncovered transcripts initiated from over half of the putative promoter fragments, and transient transfection assays revealed promoter activity for a significant proportion of fragments when they were fused to a luciferase reporter gene. These results demonstrate the specificity of a genome-wide analysis method for mapping transcriptional regulatory elements and also indicate that a small, yet significant number of human genes remains to be discovered.
Output: Direct isolation and identification of promoters in the human genome.