Characterization of the intron in the phage T4 thymidylate synthase gene and evidence for its self-excision from the primary transcript.
The td gene contains a 735 bp open reading frame within its 1017 bp intron. A 12 nucleotide stretch may form a stable secondary structure with the putative Shine-Dalgarno sequence of the intron open reading frame and thus impair its translation. SP6 RNA polymerase transcripts of the td gene synthesized in vitro at 40 degrees C encompass a 2.7 kb primary transcript, a 1.7 kb mRNA, and a 1 kb intron RNA. The excised intron RNA consisted of linear and cyclized forms. RNAase H studies and resistance of the cyclized intron to linearization by HeLa cell debranching enzyme suggest it to be circular. Self-splicing of isolated td primary transcript occurred only marginally at 28 degrees C, but increased progressively to 50 degrees C, and required the presence of both Mg++ and a guanosine cofactor. An internal guide sequence is evident which may align the 5' splice site with the 3' end, presumably for precise exon ligation.
F K
FK
Chu
G F
GF
Maley
D K
DK
West
M
M
Belfort
F
F
Maley
D001483:Base Sequence; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D005796:Genes; D005814:Genes, Viral; D006151:Guanosine / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D009690:Nucleic Acid Conformation; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism; D012367:RNA, Viral / Q000378:metabolism; D013604:T-Phages / Q000235:genetics*; D013940:Thymidylate Synthase / Q000235:genetics*; D014764:Viral Proteins / Q000235:genetics*
D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins; D006151:Guanosine; D013940:Thymidylate Synthase; D012321:DNA-Directed RNA Polymerases; D008274:Magnesium