Abstract: A transformed yeast cell containing the following DNA sequences,an HIV tat gene coding for a TAT protein,a first promoter exercising transcriptional control over the tat gene,an HIV regulatory control sequence which is responsive to the TAT protein,a pre-selected gene coding for a desired polypeptide or protein, the pre-selected gene being under the control of the HIV regulatory control sequence, anda second promoter exercising transcriptional control over the HIV regulatory control sequence and the pre-selected gene.Preferably the first and second promoters are yeast promoters, the transformed yeast cell is a S.cerevisiae cell and the HIV regulatory control sequence is a TAT responsive TAR sequence.The transformed yeast cells may be used to screen for agents that inhibit the function of TAT protein.

Abstract: Improved secretion of heterologous proteins by hosts such as yeast by using promoters of at most intermediate strength with heterologous DNA secretion signal sequences is disclosed. A promoter of at most intermediate strength, such as the actin (ACT) or iso-1-cytochrome c (CYC1) promoter in S. cerevisiae is operatively linked to a DNA signal sequence, such as the Mf.alpha.1 signal sequence. A DNA sequence for a selected protein, such as somatomedin C (SMC), tissue plasminogen activator (TPA) or tumor necrosis factor (TNF), may be operatively linked to the DNA signal sequence.