Abstract: The present invention relates to a DNA cassette intended for the transformation of yeast, leaving no useless exogenous DNA but the gene(s) of interest comprising at least one negative dominant marker, two direct repeat sequences (DRS) which are non exogenous and non recombinogenic with the genome of the host strain, these two direct repeat sequences flanking the negative dominant marker and optionally at least one gene of interest containing, if necessary, the elements necessary for its expression in the host cell. The invention relates as well to a method of integration of gene(s) of interest or inactivation of a gene in yeast, and of transformation of yeast with the DNA cassette, and to yeast strains thus obtained.

Abstract: The present invention provides novel nucleic acid fragments isolated from the genomic DNA of yeast and having transcription promoter activity, as well as expression cassettes, vectors, and host cells containing said nucleic acid fragments. The present invention also provides methods for incorporating the nucleic acid fragments of the present invention for producing commercially or therapeutically useful polypeptides.