Identification and characterization of a family of 11-kDa proteins encoded by the human parvovirus B19.

The human pathogenic parvovirus B19 directs the synthesis of two size classes of small abundant RNAs. It is shown that the smallest RNAs, of 500 and 600 nt, are translated into at least two 11-kDa proteins in B19-infected human leukemic bone marrow cells. A COS-7 cell expression system was used to demonstrate that the different forms of the protein result from translational initiation at multiple AUG codons in the same 94 aa ORF. The 11-kDa proteins were localized to the cytoplasm of transfected COS-7 cells using indirect immunofluorescence. However, their localization was at least partially nuclear in B19-infected cells. In COS-7 cells the expression of the major B19 structural and nonstructural proteins was not affected in the absence of the expression of the 11-kDa proteins.