The present invention relates to a polynucleotide comprising at least one promoter and an S/MAR element, wherein said S/MAR element is located downstream of said promoter and wherein the nucleic acid sequence of said S/MAR element (S/MAR sequence) comprises at least 3sequence motifs ATTA (SEQ ID NO : 1) per 100 nucleotides over a stretch of at most 200 nucleotides; the present invention further relates to a composition and to a host cell comprising said polynucleotide, and to the polynucleotide for use in medicine and for use in treating genetic disease. The present invention also relates to a kit and to a device comprising said polynucleotide, and to methods and uses related to the polynucleotide.