Cellular Proteins Are Enriched in Nucleolus after Adenovirus Infection-That we detected cellular proteins enriched in the nucleolus was intriguing, and this was reflected in changes in distribution of p87 PIKAP and S15a by immunofluorescence (Fig. 4, B and C) . That ribosomal protein S15a is enriched in the nucleus/nucleolus during infection again may reflect eventual interference by adenovirus with aspects of rRNA maturation and/or export.