Hierarchies of RNA-processing signals in a trypanosome surface antigen mRNA precursor.
Nearly all trypanosome mRNAs are synthesized as polycistronic precursors, from which mature mRNAs are excised by trans splicing and polyadenylation. Polyadenylation of a procyclic acidic repetitive protein (PARP, or procyclin) transcript was studied by transient transfection of constructs bearing a chloramphenicol acetyltransferase gene linked to the PARP intergenic region. Polyadenylation usually occurred at A residues, about 100 bases upstream of a trans-splicing acceptor signal. The wild-type polyadenylation site has a cryptic trans-splicing signal about 100 bp downstream: deletion or inversion of this signal results in polyadenylation at multiple sites, upstream of other cryptic trans-splicing signals. The PARP mRNA precursor appears to contain a hierarchy of possible processing signals, the function of cryptic ones being revealed only when the dominant ones are deleted or moved. Correct polyadenylation can be restored by addition of trans-splicing signals from other loci. The results indicate that polyadenylation is coupled to downstream trans splicing but that the products of the trans-splicing reaction are not necessarily functional mRNAs.
Hug
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M
Zentrum für Molekulare Biologie, Heidelberg, Federal Republic of Germany.
Hotz
H R
HR
Hartmann
C
C
Clayton
C
C
D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D008969:Molecular Sequence Data; D011061:Poly A / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012326:RNA Splicing; D016053:RNA, Protozoan / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
D000953:Antigens, Protozoan; D017931:DNA Primers; D016054:DNA, Protozoan; D012322:RNA Precursors; D016053:RNA, Protozoan; D011061:Poly A