Transcription of a nematode U1 small nuclear RNA in vitro. 3'-end formation requires cis-acting elements within the coding sequence.
We have used block-substitution mutagenesis and in vitro transcription assays to identify cis-acting DNA sequence elements important for initiation and 3'-end formation of a U1 small nuclear RNA (snRNA) in the parasitic nematode Ascaris lumbricoides. Efficient initiation of synthesis by RNA polymerase II requires a compact element centered approximately 50 base pairs upstream of the transcriptional start site. Surprisingly, 3'-end formation of U1 snRNAs synthesized in vitro is solely dependent upon elements within the U1 coding sequence. In all other systems studied thus far, 3'-end formation of U snRNAs requires signals present in the 3'-flanking region. We also show that sequence elements that direct 3'-end formation of the A. lumbricoides trans-spliced leader RNA function when RNA synthesis is initiated from the U1 promoter. These results indicate that 3'-end formation of U snRNAs in nematodes is mechanistically distinct from the analogous process in higher eukaryotes.
Hannon
G E
GE
Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
Hannon
G J
GJ
Maroney
P A
PA
Nilsen
T W
TW
D000818:Animals; D017164:Ascaris lumbricoides / Q000235:genetics*; D001483:Base Sequence; D004247:DNA; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012342:RNA, Small Nuclear / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic
D012342:RNA, Small Nuclear; D004247:DNA