the invention comprises novel polynucleotides , and related vectors , host cells , methods , and compositions , containing transcriptional enhancers providing very high levels of expression of operably - linked expressible nucleic acid sequences in eukaryotic cells . advantageously the enhancers may be used in combination with their naturally - associated promoters and / or other genetic elements that increase transcription . the invention comprises eukaryotic expression vectors that are capable of providing increased levels of expression in many cell types over that obtainable from human or murine cmv ie enhancer / promoter elements .