A novel type of splicing enhancer regulating adenovirus pre-mRNA splicing.
Splicing of the adenovirus IIIa pre-mRNA is subjected to a temporal regulation, such that efficient IIIa 3' splice site usage is confined to the late phase of the infectious cycle. Here we show that IIIa pre-mRNA splicing is activated more than 200-fold in nuclear extracts prepared from late adenovirus-infected cells (Ad-NE) compared to uninfected HeLa cell nuclear extracts (HeLa-NE). In contrast, splicing of the beta-globin pre-mRNA is repressed in Ad-NE. We constructed hybrid pre-mRNAs between IIIa and beta-globin in order to identify the minimal IIIa sequence element conferring enhanced splicing in Ad-NE. Using this approach, we show that the IIIa branch site/pyrimidine tract functions as a Janus element: it blocks splicing in HeLa-NE and functions as a splicing enhancer in Ad-NE. Therefore, we named this sequence the IIIa virus infection-dependent splicing enhancer (3VDE). This element is essential for regulated IIIa pre-mRNA splicing in Ad-NE and sufficient to confer an enhanced splicing phenotype to the beta-globin pre-mRNA in Ad-NE. We further show that the increase in IIIa splicing observed in Ad-NE is not accompanied by a similar increase in U2AF binding to the IIIa pyrimidine tract. This finding suggests that splicing activation by the 3VDE may operate without efficient U2AF interaction with the pre-mRNA. Importantly, this report represents the first description of a splicing enhancer that has evolved to function selectively in the context of a virus infection, a finding that adds a new level at which viruses may subvert the host cell RNA biosynthetic machinery to facilitate their own replication.
Mühlemann
O
O
Department of Medical Biochemistry and Microbiology, BMC, Uppsala University, S-751 23 Uppsala, Sweden.
Yue
B G
BG
Petersen-Mahrt
S
S
Akusjärvi
G
G
D000256:Adenoviridae / Q000235:genetics*; D015967:Gene Expression Regulation, Viral / Q000235:genetics*; D005914:Globins / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D009687:Nuclear Proteins; D012322:RNA Precursors / Q000378:metabolism*; D012326:RNA Splicing; D012367:RNA, Viral / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics; D016914:Ribonuclease H / Q000378:metabolism; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000378:metabolism; D012261:Ribonucleoproteins / Q000235:genetics; D000072668:Splicing Factor U2AF
D009687:Nuclear Proteins; D012322:RNA Precursors; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D017413:Ribonucleoprotein, U2 Small Nuclear; D012261:Ribonucleoproteins; D000072668:Splicing Factor U2AF; C000607494:U2AF2 protein, human; D005914:Globins; D016914:Ribonuclease H