Comparison of the transcription profile of simian parvovirus with that of the human erythrovirus B19 reveals a number of unique features.

Simian parvovirus (SPV) is a member of the genus Erythrovirus and is closely related to the human parvovirus B19. Natural and experimental infection of monkeys with SPV resembles B19 infection of human. We report a detailed characterization of the viral RNAs and proteins generated following transfection of cloned SPV into COS cells and SPV infection of the human erythroid progenitor line UT-7/Epo-S1. SPV and B19 are 50% identical at the nucleotide level, and although their basic transcription and protein expression profiles were generally similar, there were also significant differences. SPV pre-mRNAs contain three introns, compared to two found for B19: an additional intron was found within the capsid-coding region. RNAs in which this intron was spliced were abundant and encoded the SPV 14-kDa protein (analogous to the B19 11-kDa protein), which initiated at an AUG in the exon preceding the third intron. Unlike B19, SPV RNAs were also spliced between the donor of the first intron and the acceptor of the second intron. The third intron was additionally spliced from a portion of these molecules; these mRNAs encoded the 14-kDa protein. A portion was not spliced further and encoded VP2. Like B19, SPV has a polyadenylation signal [AAUAAA (pA)p] in the middle of the genome, which directed efficient polyadenylation of both spliced and unspliced mRNAs (encoding a putative 10-kDa protein, analogous to the B19 7.5-kDa protein, and SPV NS1, respectively). The 14-kDa protein was localized to both in the nucleus and cytoplasm.