Changes in Nucleolar Proteome: Adenovirus Compared with Actinomycin D-Comparison with the response of the nucleolar proteome after transcriptional inhibition by ActD treatment (in which the flux of ϳ500 nucleolar proteins was characterized) was very revealing (29) . Comparison with our data set showed that the effect of adenovirus infection is very specific with only a limited range of proteins showing a relative change in abundance (e.g. compare our Fig. 1B with Fig.  4a of Andersen et al. (29) ). For example, although transcription inhibition by ActD causes depletion of ribosomal proteins of the 40 S subunit and, to a lesser extent, the 60 S subunit (29) , this pattern was not observed in viral infection (Fig. 1D) . This was interesting because adenovirus has been shown to eventually affect ribosomal RNA export (2) . However, our chosen time point of 18 h postinfection is the earliest time that such defects in rRNA export can be detected (2) . As such, it is probable that defects in processing or export of ribosomal proteins may be only just beginning at this time point and are therefore not yet readily detectable by our methods.