Abstract: Described herein are compositions and methods for identifying, selecting, or culturing cells comprising a subject nucleic acid sequence of interest. Generally, a nucleic acid comprising a subject nucleic acid and a sequence encoding an enzyme molecule involved in biosynthesis of an amino acid is introduced into a cell. The cell is then grown on media lacking the amino acid, such that cells comprising the introduced nucleic acid are capable of growth. In some instances, the cell further comprises an inhibitor of the enzyme molecule to increase the stringency of the selection.

Abstract: Described herein are compositions and methods for identifying, selecting, or culturing cells comprising a subject nucleic acid sequence of interest. Generally, a nucleic acid comprising a subject nucleic acid and a sequence encoding an enzyme molecule involved in biosynthesis of an amino acid is introduced into a cell. The cell is then grown on media lacking the amino acid, such that cells comprising the introduced nucleic acid are capable of growth. In some instances, the cell further comprises an inhibitor of the enzyme molecule to increase the stringency of the selection.

Abstract: Described herein are production cells, and methods for identifying, selecting, or culturing production cells comprising tyrosine auxotrophy selection marker system, based on a combination of sequence encoding a phenylalanine hydroxylase (PAH) which lacks a functional N-terminal regulatory domain, and a sequence encoding a GTP cyclohydrolase 1 (GCH1). Also described are methods of making a production cell and making a product with said production cell.