We analyzed the expression of 10 genes representative of the ribosome biogenesis pathway (HEATR1, WDR43, DDX21 and UTP20 described above and other 6 genes found down-regulated in the RNA-seq analysis at lesser extent) by RT-qPCR using total RNA isolated from, mock-infected and infected samples (the same RNA employed in the RNA-seq and RNA isolated from other two independent infection experiments) and confirmed the decrease in the accumulation of the mRNA level of these genes associated with the nucleolus upon infection with HIV-1 (Figure 2a). This evidence concerns the gene DDX21 and infection.