Polynucleotides, vectors, systems of vectors or polynucleotides, cells, and methods for expressing AAV Rep and Cap proteins are provided. In certain aspects, these polynucleotides, cells, and methods may produce higher levels of one or both of Rep and Cap transcripts. In some aspects, these polynucleotides, cells, and methods may produce higher levels of one or both of Rep and Cap proteins. In various aspects, these polynucleotides, vectors, systems of vectors or polynucleotides, cells, and methods use one or more
heterologous polyA sequences with one or both of the Rep and Cap coding sequences. In numerous aspects, these polynucleotides, vectors, systems of vectors or polynucleotides, cells, and methods may use one or more enhancers to increase expression of Rep proteins, where such enhancers can be transcriptional enhancers, translational enhancers, or combinations thereof. In certain aspects, these polynucleotides, vectors, systems of vectors or polynucleotides, cells, and methods may be used to produce recombinant AAV (rAAV).