pCAGGS is a mammalian protein expression vector

pCAGGS is a mammalian gene expression vector that consists of the combination of cytomegalovirus enhancer and chicken beta actin promoter associated with the rabbit poly A signal under the multicloning site. Some genes that cannot be expressed under the cytomegalovirus promoter are sometimes expressed by using pCAGGS vector. Is there a relationship between the kinds of genes and their favorite expression vector? I don't know that. Recently, I was impressed with a success that I could let a viral polymerase protein express by using pCAGGS, whereas the protein didn't be expressed under the CMV promoter.