Chimeric single-stranded polynucleotides and double-stranded antisense agents useful for modifying the expression of a target gene by means of an antisense effect are disclosed. The chimeric single-stranded antisense polynucleotide and double-stranded antisense agents comprise a central nucleotide region flanked by a first 5&prime；-wing region and a first 3&prime；-wing region of modified nucleotides, which are themselves flanked by a second 5&prime；-wing region and/or a second 3&prime；-wing region of nucleotides that have a low affinity for proteins and/or that have higher resistance to DNase or RNase than a natural DNA or RNA and are missing in a cell when the chimeric polynucleotide delivered. The double-stranded antisense agent further comprises a complementary strand annealed to the antisense strand. The polynucleotide can be used to modify RNA transcription levels, miRNA activity, or protein levels in cells.
