Figure 2.

Expression analysis as a function of total 5'UTR intron length. (a) Heat map of the mean expression level versus the total 5'UTR intron length. The shade of gray represents the number of transcripts in each bin with darker shades implying more transcripts. The overrepresentation of short 5'UTR-intron-containing genes among the highest expression levels is apparent. (b) Quantile-quantile plot of total 5'UTR intron length of short 5'UTR intron-containing genes divided into highly expressed (top 5%) and other genes. The most highly expressed genes tend to have shorter 5'UTR introns. (c) Smoothed histogram of the mean expression level with respect to presence/absence of 5'UTR intron and its length. A kernel density estimator was fitted to the expression data and the corresponding probability density is plotted as a function of the mean expression level. The black line corresponds to the probability density for transcripts without any 5'UTR introns. Genes with long 5'UTR introns are represented by the red line while genes with short 5'UTR introns are represented by the blue line. The vertical line represents the top 5% of mean expression level of all genes. (d) Total 5'UTR intron length of genes in different expression level categories. The width of the boxes represents the relative number of data points in each category. Transcripts in the top 1% and top 5% in expression level tend to have shorter 5'UTR introns.