Filing Date: 2003-01-24.--Priority Data: ES (2002-01-24) (P200-20-01)The invention relates to a nucleic acid sequence comprising the RNA packaging signal of a group 1 coronavirus, such as transmissible gastroenteritis virus of swine (TGEV), which is located between nucleotides 100 and 649 of the genome of said coronavirus. The inventive sequence can be employed to produce viral vectors for use in basic and applied research, for example, in developing systems of expressing products of interest, vaccine vectors and gene therapy.