Biomedical subjects

Fulai Jin

Publications and source records attributed to Fulai Jin.

5 recordsLinked to original sources

PubMed2026

Rapid reduction in global chromatin loop size after acute STAG2 reconstitution in human cancer cells.

Truncating mutations in the tumor suppressor STAG2, which encodes a component of the cohesin complex, are prevalent across diverse human cancers. Here, we report that acute reconstitution of physiological STAG2 levels in STAG2-mutant human glioblastoma multiforme cancer cells triggers a rapid reduction in the size of chromatin loops genome-wide. Despite this global change in chromatin loop size, early transcriptional responses to STAG2 restoration are limited to a small number of genes, most of which are induced by STAG2 reconstitution. Notably, the growth-suppressor EFEMP1 (Fibulin-3), a secreted glycoprotein that functions as an extracellular matrix-associated inhibitor of glioblastoma growth and invasion, was the only gene consistently induced across all experimental models. The most robust and conserved STAG2-induced genes all reside within intense chromatin loops whose anchors and overall intensity did not appear to change in response to STAG2 reconstitution. These findings suggest that inactivating mutations of STAG2 promote neoplastic transformation by alleviating a restriction on chromatin loop size, allowing for an expanded range of chromatin interactions that disrupts the maintenance of a tumor-suppressive transcriptome.

Humans↗

PubMed2026

Proinsulin regulators identified with CRISPR screen and in vivo mouse QTL mapping.

Altered proinsulin levels in β-cells and bloodstream are hallmarks of diabetes and other diseases, but our knowledge about the proinsulin regulators remains limited. Here we perform a genome-wide CRISPR screen to identify 84 proinsulin regulators that alter intracellular proinsulin/insulin ratio in a mouse β-cell line. The proinsulin regulators are distinct from the insulin regulators from a previous orthogonal CRISPR screen. Functional annotation of the proinsulin regulators highlights Golgi as the primary organelle for proinsulin storage and regulation. Trafficking towards the Golgi increases the intra-cellular proinsulin/insulin ratio, while trafficking away from the Golgi, including exocytosis and Golgi-to-ER retrograde transport, decreases the intracellular proinsulin levels. We also map mouse quantitative trait loci (QTLs) associated with plasma proinsulin levels and use the CRISPR screen results to pinpoint the causal genes within the QTL loci. Interestingly, protein disulfide isomerase Pdia6 is the strongest hit from both CRISPR screen and the in vivo QTL mapping. Knocking down Pdia6 significantly reduce proinsulin accumulation in Golgi and secretory granules. Intriguingly, Pdia6-depletion in both human and mouse β-cells does not affect the folding status of proinsulin but causes significantly impaired proinsulin production through a UPR-independent mechanism. Taken together, our genetic profiles provide mechanistic insights into the regulation of proinsulin/insulin homeostasis.

Animals↗

PubMed2006

A pooling-deconvolution strategy for biological network elucidation.

The generation of large-scale data sets is a fundamental requirement of systems biology. But despite recent advances, generation of such high-coverage data remains a major challenge. We developed a pooling-deconvolution strategy that can dramatically decrease the effort required. This strategy, pooling with imaginary tags followed by deconvolution (PI-deconvolution), allows the screening of 2(n) probe proteins (baits) in 2 x n pools, with n replicates for each bait. Deconvolution of baits with their binding partners (preys) can be achieved by reading the prey's profile from the 2 x n experiments. We validated this strategy for protein-protein interaction mapping using both proteome microarrays and a yeast two-hybrid array, demonstrating that PI-deconvolution can be used to identify interactions accurately with fewer experiments and better coverage. We also show that PI-deconvolution can be used to identify protein-small molecule interactions inferred from profiling the yeast deletion collection. PI-deconvolution should be applicable to a wide range of library-against-library approaches and can also be used to optimize array designs.

Computational Biology↗

PubMed2005

Insights into TOR function and rapamycin response: chemical genomic profiling by using a high-density cell array method.

With the advent of complete genome sequences, large-scale functional analyses are generating new excitement in biology and medicine. To facilitate genomewide functional analyses, we developed a high-density cell array with quantitative and automated readout of cell fitness. Able to print at > x 10 higher density on a standard microtiter plate area than currently possible, our cell array allows single-plate screening of the complete set of Saccharomyces cerevisiae gene-deletion library and significantly reduces the amount of small molecules and other materials needed for the study. We used this method to map the relation between genes and cell fitness in response to rapamycin, a medically important natural product that targets the eukaryotic kinase Tor. We discuss the implications for pharmacogenomics and the uncharted complexity in genotype-dependent drug response in molecularly targeted therapies. Our analysis leads to several basic findings, including a class of gene deletions that confer better fitness in the presence of rapamycin. This result provides insights into possible therapeutic uses of rapamycin/CCI-779 in the treatment of neurodegenerative diseases (including Alzheimer's, Parkinson's, and Huntington's diseases), and cautions the possible existence of similar rapamycin-enhanceable mutations in cancer. It is well established in yeast that although TOR2 has a unique rapamycin-insensitive function, TOR1 and TOR2 are interchangeable in the rapamycin-sensitive functions. We show that even the rapamycin-sensitive functions are distinct between TOR1 and TOR2 and map the functional difference to a approximately 120-aa region at the N termini of the proteins. Finally, we discuss using cell-based genomic pattern recognition in designing electronic or optical biosensors.

Cell Cycle Proteins↗

PubMed2004

Finding new components of the target of rapamycin (TOR) signaling network through chemical genetics and proteome chips.

The TOR (target of rapamycin) proteins play important roles in nutrient signaling in eukaryotic cells. Rapamycin treatment induces a state reminiscent of the nutrient starvation response, often resulting in growth inhibition. Using a chemical genetic modifier screen, we identified two classes of small molecules, small-molecule inhibitors of rapamycin (SMIRs) and small-molecule enhancers of rapamycin (SMERs), that suppress and augment, respectively, rapamycin's effect in the yeast Saccharomyces cerevisiae. Probing proteome chips with biotinylated SMIRs revealed putative intracellular target proteins, including Tep1p, a homolog of the mammalian PTEN (phosphatase and tensin homologue deleted on chromosome 10) tumor suppressor, and Ybr077cp (Nir1p), a protein of previously unknown function that we show to be a component of the TOR signaling network. Both SMIR target proteins are associated with PI(3,4)P2, suggesting a mechanism of regulation of the TOR pathway involving phosphatidylinositides. Our results illustrate the combined use of chemical genetics and proteomics in biological discovery and map a path for creating useful therapeutics for treating human diseases involving the TOR pathway, such as diabetes and cancer.

Humans↗