Ontology highlight
ABSTRACT:
PROVIDER: PRJNA1172643 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR30994000_1.fastq.gz | Fastqsanger.gz | |||
| SRR30994000_2.fastq.gz | Fastqsanger.gz | |||
| SRR30994001_1.fastq.gz | Fastqsanger.gz | |||
| SRR30994001_2.fastq.gz | Fastqsanger.gz | |||
| SRR30994002_1.fastq.gz | Fastqsanger.gz |
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Project description:Pre mRNA 3 end processing is unique in trypanosomes as it involves polycistronic transcription, polyadenylation coupled to trans splicing and elusive polyadenylation signals. The mechanism is poorly understood. Here we reported that nine putative polyA factors from Trypanosoma brucei form a stable complex which then subsequently develops into two tight subcomplexes. One contains the proteins tbCPSF160, tbCPSF30, tbFip1 and tbWdr33 with tbCPSF160 as the scaffold; while the other contains tbCPSF100, tbCPSF73, tbSYMK and two trypanosome unique proteins, designated CPF30 and CPF15. No CstF homologs were found. The protein tbCPSF100 seems to coordinate the association of these two subcomplexes by interacting with tbCPSF160. RNAi knockdown of these polyA factors resulted in RNA processing disorders and variable disruption of the complex and RNA processing disorders. Depletion of either factors caused dicistronic transcripts formation; depletion of either tbCPSF30, tbFip1 or tbWdr33 caused increased usage of proximal polyadenylation sites of the transcripts; depletion of tbCPSF30 caused mRNA polyA tail shortening. This indicates that these two polysA factors have a critical role in polyadenylation site selection. Genome-wide UV crosslinking assays showed that tbCPSF30 and tbFip1 have strong RNA-binding activity in this complex. Altogether, these data indicate that the 3 end processing complex of T. brucei is more like the human CPSF homolog. However, it displays trypanosome specific features in composition, structural assembly and function of components, which facilitate a common, yet unique, cleavage polyadenylation reaction.
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Project description:Trypanosoma brucei is a protozoan parasite that causes human African trypanosomiasis. Its major surface antigen VSG is expressed from subtelomeric loci in a strictly monoallelic manner. We previously showed that the telomere protein TbRAP1 binds dsDNA through its 737RKRRR741 patch to silence VSGs globally. How TbRAP1 permits transcription of the single active VSG is unknown. Through NMR structural analysis, we unexpectedly identify an RNA Recognition Motif (RRM) in TbRAP1, which is unprecedented for RAP1 homologs. Assisted by the 737RKRRR741 patch, TbRAP1 RRM recognizes consensus sequences of VSG 3’UTRs in vitro and binds the active VSG RNA in vivo. Mutating conserved RRM residues abolishes the RNA binding activity, significantly decreases the active VSG RNA level, and derepresses silent VSGs. The competition between TbRAP1’s RNA and dsDNA binding activities suggests a novel mechanism of monoallelic expression, in which the active VSG’s abundant RNA antagonizes TbRAP1’s silencing effect, thereby sustaining its full-level transcription.
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Project description:MicroRNAs (miRNAs) are small regulatory RNAs processed from stem-loop regions of primary transcripts (pri-miRNAs), with the choice of stem-loops for initial processing largely determining what becomes a miRNA. To identify sequence and structural features influencing this choice, we determined cleavage efficiencies of >50,000 variants of three human pri-miRNAs, focusing on the regions intractable to previous high-throughput analyses. Our analyses revealed a mismatched motif in the basal stem region, a preference for maintaining or improving base-pairing throughout the remainder of the stem, and a narrow stem-length preference of 35±1 base pairs. Incorporating these features with previously identified features, including three primary-sequence motifs, yielded a unifying model defining mammalian pri-miRNAs, in which motifs help orient processing and increase efficiency, with the presence of more motifs compensating for structural defects. This model enables generation of artificial pri-miRNAs, designed de novo, without reference to any natural sequence, yet processed more efficiently than natural pri-miRNAs. Three major experiments are included in the submitted data. 1) Pools of synthetic DNA containing barcodes and pri-miRNA variants were sequenced to infer the barcode-pri-miRNA linkages, and the pri-miRNA variants were assayed for their cleavage efficiency ("selection"), which can be quantified by comparing their representations in the input and after cleavage. 2) Artificial miRNAs produced in HEK293T cells were sequenced. 3) Transcriptomes of artificial miRNA-expressed cells were sequenced to quantify mRNA changes.
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