FIGURE 10-26 Transport of HIV mRNAs from the nucleus to the cytoplasm. The HIV genome, which contains several coding regions, is transcribed into a single 9-kb primary transcript. Several 4-kb mRNAs result from the splicing out of any one of several introns (dashed lines), and several 2-kb mRNAs result from the splicing out of two or more alternative introns. After transport to the cytoplasm, these various RNA species are translated into different viral proteins. Rev protein, encoded by a 2-kb mRNA, interacts with the Rev-response element (RRE) in the unspliced and singly spliced mRNAs, stimulating their transport to the cytoplasm. See B. R. Cullen and M. H. Malim, 1991, Trends Biochem. Sci. 16:346.