Abstract: Disclosed herein is an isolated polynucleotide molecule encoding protein such as erythropoietin or structural variants, comprising an expression regulating nucleotide sequence operatively linked to a nucleotide sequence(s) encoding said proteins. The said expression regulatory region comprises of Exon A and at least proximal region of Intron A of Major Immediate Early Region of human Cytomegalovirus or its functional variants which when transfected into host cells results in many fold increase in expression of the protein.