Numerous Fragmented Spliceosomal Introns, AT-AC Splicing, and an Unusual Dynein Gene Expression Pathway in Giardia lamblia
Bibliographic record
Abstract
Spliceosomal introns are hallmarks of eukaryotic genomes, dividing coding regions into separate exons, which are joined during mRNA intron removal catalyzed by the spliceosome. With few known exceptions, spliceosomal introns are cis-spliced, that is, removed from one contiguous pre-mRNA transcript. The protistan intestinal parasite Giardia lamblia exhibits one of the most reduced eukaryotic genomes known, with short intergenic regions and only four known spliceosomal introns. Our genome-wide search for additional introns revealed four unusual cases of spliceosomal intron fragmentation, with consecutive exons of conserved protein-coding genes being dispersed to distant genomic sites. Independent transcripts are trans-spliced to yield contiguous mature mRNAs. Most strikingly, a dynein heavy chain subunit is both interrupted by two fragmented introns and also predicted to be assembled as two separately translated polypeptides, a remarkably complex expression pathway for a nuclear-encoded sequence. For each case, we observe extensive base-pairing potential between intron halves. This base pairing provides both a rationale for the in vivo association of independently transcribed mRNAs transcripts and the apparent specificity of splicing. Similar base-pairing potential in two cis-spliced G. lamblia introns suggests an evolutionary pathway whereby intron fragmentation of cis-spliced introns is permissible and a preliminary evolutionary step to complete gene fission. These results reveal remarkably complex genome dynamics in a severely genomically reduced parasite.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".