4. All of the above.
Post-transcriptional control of gene expression occurs between the processes of transcription initiation and translation. Control of splicing results in the production of splice variants possessing different properties and activities, RNA shuttling is directly associated with the speed of mRNA delivery to ribosomes, while control of RNA stability determines the mRNA half-life and degradation. As a result, all these factors contribute to the post-transcriptional regulation of gene expression.