Looking for Organization Patterns of Highly Expressed Genes: Purine-Pyrimidine Composition of Precursor mRNAs |
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Authors: | A Paz D Mester E Nevo A Korol |
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Institution: | (1) Institute of Evolution, Haifa University, Mount Carmel, Haifa, 31905, Israel |
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Abstract: | We analyzed precursor messenger RNAs (pre-mRNAs) of 12 eukaryotic species. In each species, three groups of highly expressed
genes, ribosomal proteins, heat shock proteins, and amino-acyl tRNA synthetases, were compared with a control group (randomly
selected genes). The purine-pyrimidine (R-Y) composition of pre-mRNAs of the three targeted gene groups proved to differ significantly
from the control. The exons of the three groups tested have higher purine contents and R-tract abundance and lower abundance
of Y-tracts compared to the control (R-tract—tract of sequential purines with R
n
≥ 5; Y-tract—tract of sequential pyrimidines with Y
n
≥ 5). In species widely employing “intron definition” in the splicing process, the Y content of introns of the three targeted
groups appeared to be higher compared to the control group. Furthermore, in all examined species, the introns of the targeted
genes have a lower abundance of R-tracts compared to the control. We hypothesized that the R-Y composition of the targeted
gene groups contributes to high rate and efficiency of both splicing and translation, in addition to the mRNA coding role.
This is presumably achieved by (1) reducing the possibility of the formation of secondary structures in the mRNA, (2) using
the R-tracts and R-biased sequences as exonic splicing enhancers, (3) lowering the amount of targets for pyrimidine tract
binding protein in the exons, and (4) reducing the amount of target sequences for binding of serine/arginine-rich (SR) proteins
in the introns, thereby allowing SR proteins to bind to proper (exonic) targets.
(Reviewing
Editor: Dr. Axel Meyer) |
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Keywords: | Purine tracts Pyrimidine tracts Splicing efficiency Highly expressed genes Intron definition Exon definition |
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