*2.15. Positive Correlations among 5*′*UTR Features*

Correlations among the following independent variables: 5′UTR length, no. of uATGs, sATG flanking sequence context, no. of 5′UTR introns, length of all 5′UTR introns in a gene, presence of RG4-forming sequence, no. of stem loops, protein tissue distribution, and protein mode expression score were tested by non-parametric tests (Spearman's rs and Kendall's tau) in the first correlation analysis. Some positive correlations were found to be statistically significant (Table S3 and Figure 3). The variable 5′UTR length correlated with No. of uATGs (*p* = 0.004 and 0.006, respectively), no. of 5′UTR introns (0.037/0.016), and no. of stem loops (0.002/0.004). Furthermore, no. of uATGs correlated with no. of 5′UTR introns (0.041/0.022), sATG flanking sequence context with the presence of RG4-forming sequence (0.046/0.010), no. of 5′UTR introns with Length of all 5′UTR introns in a gene (<0.001/<0.001), and no. of stem loops with length of all 5′UTR introns in a gene (0.042/0.011). The variables protein tissue distribution and protein mode expression score did not correlate significantly with any other variable.

**Figure 3.** Correlation table plot. The circles represent the Spearman's *rs* correlation coefficients on a given scale; if the relevant *p* value is >0.05 the circle is crossed. 5′U., 5′UTR; Cont., context; Distrib., distribution; Expres., expression; Int., intron; No., number; Prot., protein; RG4, RNA G-quadruplex; sATG, start ATG of the main ORF; St., stem; uATG, upstream ATG.

The special features of uATGs-uATG position (from transcription start site, TSS), uATG conservation, uATG flanking sequence context, and uATG TIS score were tested similarly in the second correlation analysis. The variable uATG TIS score correlated positively with uATG position (0.034/0.031) and uATG flanking sequence context (0.011/0.003) (Table S4 and Figure 4).

**Figure 4.** Correlation table plot. The circles represent the Spearman's *rs* correlation coefficients on a given scale; if the relevant *p* value is > 0.05 the circle is crossed. uATG cons., uATG conservation; uATG cont., uATG flanking sequence context; uATG pos., uATG position (from transcription start site); uATG TIS sc., uATG TIS score (from NetStart).
