The invention provides for polynucleotides and vectors comprising at least two tag sequences. In particular, preferred vectors are viral vectors. The invention also provides for polynucleotides and vectors comprising a streptavidin binding peptide sequence and a calmodulin binding peptide sequence. The invention also provides for polynucleotides and vectors wherein a gene of interest is fused in frame to at least two tag sequences, for example, a streptavidin binding peptide sequence and a calmodulin binding peptide sequence. The invention also provides for methods of using the polynucleotides and vectors of the invention for detecting and/isolating protein complexes or identifying a binding partner for a protein of interest.