In vitro translation of Plasmodium falciparum aldolase is not initiated at an unusual site.

Knapp, Bernhard; Günther, Kathrin; Lingelbach, Klaus

doi:10.1002/j.1460-2075.1991.tb07862.x

Cited by 6 publications

(1 citation statement)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…falciparum introns are comparatively short and extremely AT rich, averaging 179 nucleotides (nt) and 86.5% AϩT (11). Some are located at the end of an open reading frame, adding a single amino acid (22), or in an untranslated region (UTR) (33,34). They are implicated in control of var gene expression (8), and instances of stage-specific expression, sex-specific expression, and alternative splicing have been reported (26,32,42).…”

mentioning

confidence: 99%

Branch Point Identification and Sequence Requirements for Intron Splicing in Plasmodium falciparum

et al. 2011

View full text Add to dashboard Cite

Splicing of mRNA is an ancient and evolutionarily conserved process in eukaryotic organisms, but intronexon structures vary. Plasmodium falciparum has an extreme AT nucleotide bias (>80%), providing a unique opportunity to investigate how evolutionary forces have acted on intron structures. In this study, we developed an in vivo luciferase reporter splicing assay and employed it in combination with lariat isolation and sequencing to characterize 5 and 3 splicing requirements and experimentally determine the intron branch point in P. falciparum. This analysis indicates that P. falciparum mRNAs have canonical 5 and 3 splice sites. However, the 5 consensus motif is weakly conserved and tolerates nucleotide substitution, including the fifth nucleotide in the intron, which is more typically a G nucleotide in most eukaryotes. In comparison, the 3 splice site has a strong eukaryotic consensus sequence and adjacent polypyrimidine tract. In four different P. falciparum pre-mRNAs, multiple branch points per intron were detected, with some at U instead of the typical A residue. A weak branch point consensus was detected among 18 identified branch points. This analysis indicates that P. falciparum retains many consensus eukaryotic splice site features, despite having an extreme codon bias, and possesses flexibility in branch point nucleophilic attack.Introns are noncoding sequences located inside precursor mRNA (pre-mRNA) transcripts that are excised before nuclear export (39). Splicing of pre-mRNA requires sequence motifs in the intron and is mediated by a ribonucleoprotein complex called the spliceosome (37,53). While the fundamental mechanisms of splicing are conserved among eukaryotes (4), splice site recognition motifs are short and often only weakly conserved between organisms (20). In addition, most predictive software relies on model organisms, and there has been only limited experimental characterization of intron splicing in deep-branching eukaryotic organisms (50). Introns are predicted to be present in approximately half the genes in the Plasmodium falciparum genome (11). However, inaccuracies in intron prediction have been reported (26,32,42). P. falciparum has an extremely AT-rich genome (11), which has implications for both evolutionary adaptations of the spliceosome machinery and accuracy of gene structure predictions.All spliceosomal introns contain 5Ј donor and 3Ј acceptor splice sites, usually with GU and AG dinucleotides at the respective intron ends and a branch point located within the intron. Major-class introns often contain a polypyrimidine tract adjacent to the 3Ј splice site, which is missing in minor-class introns (29,39). During splicing, the branch point nucleotide initiates a nucleophilic attack on the 5Ј donor splice site. The free end of the upstream intron then initiates a second nucleophilic attack on the 3Ј acceptor splice site, releasing the intron as an RNA lariat and covalently combining the two exons (53). Intron size variation is largely due to the distance from the intron's 5Ј bound...

show abstract