The present invention relates inter alia to expression vector production as well as application to the production of host cells for protein repertoire expression and high-throughput screening. The invention also relates to primers useful for PCR amplification of nucleotide sequences encoding human antibody variable domains.

The present invention discloses a method for assessing the capacity of a substance to treat or prevent hepadnavirus infection. A reporter virus carrying genetic information for a first fragment of a recombinase and a reporter cell expressing a second fragment of the recombinase are used. When the reporter virus infects the reporter cell, the two fragments of the recombinase associate and excise a stop cassette that is flanked by two recombination sites and blocks the expression of a reporter gene. Accordingly, the present invention relates to a method of assessing the capacity of a substance to treat or prevent hepadnavirus infection, a hepadnavirus comprising a nucleic acid encoding a first fragment of a recombinase and a mammalian hepatocyte or hepatoma cell comprising a nucleic acid encoding a second fragment of a recombinase and a nucleic acid comprising a stop cassette flanked by two recombination sites fused to a reporter gene.

Compositions and methods for identifying and using cis-regulatory and decoy sequences are disclosed.

The invention relates to a method for selecting an expressed sequence from a library, comprising the following steps: Each of a plurality of eukaryotic cells comprising a cell wall comprises a nucleic acid sequence member of a library, which is expressed as a target membrane protein in said eukaryotic cells. The cell wall of the cells is permeabilized. The permeabilized cells are labeled with a ligand capable of binding to the target membrane protein. The ligand bears a detectable label. A subset of the labelled cells is selected as a function of detectable label present. Finally, an expressed nucleic acid sequence is isolated from said selection of cells in an isolation step.

The invention features methods of identifying and validating affinity reagents, such as antibodies. The methods of the invention generally involve screening an antibody library by, for example, phage display on bacteria (e.g., E. coli) to identify particular antibody clones capable of binding a desired target polypeptide. Clones identified in this way can then be validated using yeast 2-hybrid. In some instances, antibodies identified by their capacity to binding a partial antigen can be validated by their capacity to bind to the full-length antigen. Validated clones can be further screened by additional rounds of phage display and/or yeast 2-hybrid. Between each round, additional variants of particular antibody clones can be generated and screened to identify variants that demonstrate higher binding affinity to the target of interest.

The present invention provides nucleic acid constructs, expression vectors, transgenic cell and methods of making and using the same, wherein the nucleic acid construct includes a synthetic promoter designed from the endogenous promoter of BIRC5 and LAMC2. In illustrative working embodiments of the invention, an exogenous nucleic acid fragment encoding thymidine kinase is operably linked to the synthetic promoter which is then shown to regulate the expression of this polypeptide.

A method for developing capture agents for target proteins employs a compound library to find cyclic peptide sequences that bind the target protein. The target protein is also reacted with a clickable group-provider reagent to provide the protein with clickable groups. The compounds in the library are provided with complementary clickable groups that bind the clickable group on the target protein when the peptide sequences bind the target protein. In some embodiments, the cyclic peptide sequences that bind the target protein are incorporated into constructs having one or more arms that can serve as capture agents or potential treatments against the pathogens from which the target protein is derived. Some embodiments provide pharmaceutical compositions for immunoassays, diagnostics, therapeutics or the like, that employ the constructs.

Disclosed herein, in some embodiments, non-naturally occurring proteins (e.g., non-naturally occurring modified proteins) that may be useful in the treatment of bacterial and viral infections, including SARS-CoV-2 infection, host cells comprising the same, and methods of treating bacterial and viral infections including SARS-CoV-2 infection. Also provided herein are host cells comprising fusion proteins for split intein-based selection of peptides that bind a target protein, methods of using the same, and methods of identifying peptides that bind a target protein.

Provided is a system for multiplexed genome editing or a two or three-way combinatorial CRISPR screening. Also provided is high-throughput screening of disease-alleviating genetic combinations to identify two-way and three-way synergistic drug combinations as potential treatment regimens. Also provided is a lentiviral three-way combinatorial guide RNA expression cassette and combinatorial guide RNA libraries.

The present invention discloses a sequencing library comprising a nucleotide sequence. The sequence comprises a linker sequence and two target sequences. Two ends of the linker sequence are respectively linked to the target sequences and the two target sequences are direct repeat sequences. The present invention further discloses preparation and use of the sequencing library. The present invention overcomes the high error rate problem of current DNA sequencing technologies, especially in a way of very low coverage bias, and can be used to detect low frequency mutations in different kinds of samples.