The presently disclosed subject matter relates to targeted integration (TI) host cells suitable for the expression of recombinant proteins wherein those TI host cells have been subjected to supertransfection resulting in the random integration (RI) of exogenous nucleic acids encodes into their genome, as well as methods of producing and using said supertransfected TI host cells.

Provided herein are compositions and methods for studying cancer therapeutics and etiology, for example, mouse cancer models, cancer cell lines, and uses thereof. Human p53 knock-in (Hupki) mice with a Y220 (e.g., Y220C, Y220H, or Y220S) mutation in p53 are provided. These Hupki-Y220 mice can be used, for example, to examine tumorigenesis in different tissues, investigate mechanisms of gain of function, develop mouse models of cancer, generate cancer cell lines that can be implanted into recipient mice, and test potential therapeutics.

Novel lentivirus packaging systems engineered with a synthetic gene network having a positive feedback loop to amplify the expression of virus genes are provided. When co-transfected into a host cell with a transfer plasmid and envelope vector, extremely high viral titers are achieved when compared to transfection of a host cell with conventional third generation packaging systems. Methods for enhancing production of lentivirus, compositions comprising high titer lentivirus, and therapeutic methods based on delivery of lentiviral nucleic acid to target cells are also provided.

Recombinant expression vectors are disclosed that include a control sequence for recombinant expression of proteins of interest; the control sequence combines a mCMV enhancer sequence with a rat EF-1alpha intron sequence. Some of the vectors are useful for tetracycline-inducible expression. Some of the vectors contain a 5′ PiggyBac ITR and a 3′ PiggyBac ITR to promote genomic integration into a host cell chromosome. A method of selecting a stable production cell line for manufacturing a protein of interest is also disclosed. Also disclosed are mammalian host cells comprising the inventive recombinant expression vectors and a method of producing a protein of interest, in vitro, involving the mammalian host cell.

Disclosed herein are flavivirus signal peptide mutants useful for enhancing the production and secretion of flavivirus envelope (E) viral proteins or virus-like proteins. Also disclosed herein are methods of vaccinating subjects (e.g., human subjects) against a flavivirus comprising administering an expression vector, wherein the expression vector comprises a polynucleotide, and a fusion polypeptide comprising an engineered signal peptide and a flavivirus envelope (E) protein

Novel lentivirus packaging systems engineered with a synthetic gene network having a positive feedback loop to amplify the expression of virus genes are provided. When co-transfected into a host cell with a transfer plasmid and envelope vector, extremely high viral titers are achieved when compared to transfection of a host cell with conventional third generation packaging systems. Methods for enhancing production of lentivirus, compositions comprising high titer lentivirus, and therapeutic methods based on delivery of lentiviral nucleic acid to target cells are also provided.

The present invention encompasses compositions and methods to rejuvenate cells by, expanding the replicative life span of the cells for, e.g., use in regenerative therapies. Specifically, the methods and compositions of the present invention increase the proliferation capacity and differentiation capacity and plasticity of cells.

Provided are a targeting vector, a nucleic acid composition, and a method for constructing a liver-injured mouse model. The targeting vector includes a first expression cassette and a second expression cassette located downstream of the first expression cassette, the first expression cassette has the following elements connected in series in sequence: a liver-specific promoter, a tetracycline transcription activation regulating factor, and a first polyA; and the second expression cassette has the following elements connected in series in sequence: a second polyA, a mouse prourokinase activator encoding gene, and a tetracycline-inducible promoter. The liver-injured mouse model constructed with this targeting vector has the phenotype of spontaneously generating the liver injury and aggravating the liver injury by induction, which provides liver-injured mouse models for studies of liver diseases.

Methods are provided for altering target DNA in a cell genetically modified to express a Cas 9 enzyme that forms a co-localization complex with a guide RNA complementary to the target DNA and that cleaves the target DNA in a site specific manner. Methods include introducing into the cell a first foreign nucleic acid encoding a donor nucleic acid sequence, introducing into the cell from media surrounding the cell the guide RNA complementary to the target DNA and which guides the Cas 9 enzyme to the target DNA, wherein the RNA and the enzyme are members of a co-localization complex for the target DNA, wherein the donor nucleic acid sequence is expressed, wherein the guide RNA and the Cas 9 enzyme co-localize to the target DNA, the Cas 9 enzyme cleaves the target DNA and the donor nucleic acid is inserted into the target DNA to produce altered DNA in the cell.

Synthetic gene circuits and methods for modeling complex spatial patterns (for example, in somitogenesis) and related plasmids are disclosed herein. Also disclosed herein are methods of generating an expression pattern using the synthetic gene circuit described herein.