Figure 4. Genetic organization of generalized provirus.

Figure 4

Genetic organization of generalized provirus. The proviral DNA as it is inserted into host DNA is shown at the top, with the long terminal repeats (LTRs) composed of U3, R, and U5 elements at each end abutting cellular sequences. Sequences in the LTR that are important for transcription, for example, enhancers, the promoter, and the poly(A) addition signal, are marked. The gag, pro, pol, and env sequences are located invariably in the positions shown in all retroviruses. Accessory genes are located as shown, and also overlapping env and U3 and each other, and occasionally in other locations. The RNA that is the primary transcriptional product is shown on the second line. Sequences that are important for replication and gene expression are shown in the approximate locations in which they are typically found. (PBS) Primer-binding site; (ψ) encapsidation sequence; (SD) splice donor site; (FS) frameshift site; (SA) splice acceptor site; (PPT) polypurine tract; (PA) polyadenylation signal; (AAA) poly(A) tail. The spliced messenger RNA for the Env protein is shown on the third line. Retroviruses with accessory genes have other spliced mRNAs and thus other splice donor and splice acceptor sites as well.

From: Genetic Organization

Cover of Retroviruses
Coffin JM, Hughes SH, Varmus HE, editors.
Cold Spring Harbor (NY): Cold Spring Harbor Laboratory Press; 1997.
Copyright © 1997, Cold Spring Harbor Laboratory Press.

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