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Table 6 The ability of each set of ESEs to predict trends in relative synonymous codon usage

From: The evolution, impact and properties of exonic splice enhancers

Dataset

Negatives

Positives

Pbinomial

Rho

Pcorr

Chi2

Poverall

ESR

54

33

0.016

-0.21

0.056

14.04

<0.001

INT2

46

41

0.33

-0.18

0.1

6.82

<0.05

INT2.400

57

30

0.0025

-0.14

0.2

15.2

<0.0005

INT3

56

31

0.0048

-0.24

0.027

17.90

<0.0005

INT3.400

60

27

0.00026

-0.18

0.1

21.11

<0.0001

Ke-ESE

23

64

1

0.0015

0.99

0.02

ns

Ke-ESE400

23

64

1

-0.091

0.4

1.83

ns

PESE

49

38

0.14

0.00033

1

3.93

ns

RESCUE

66

21

7.10E-07

-0.31

0.0031

39.9

<0.0000001

  1. Here was ask whether: (a) each ESE dataset can predict which of two synonymous codons is preferred near a boundary and which is relatively preferred in ESEs, assayed by their HPI scores; and (b) whether the extent of the difference in tendency to be found in ESEs predicts the degree of difference in the preference as one approaches exon ends. Regarding the first aspect, the expectation is that, orientating all comparisons such that the difference in HPI >0, the difference in slope should be negative. We thus ask whether there are more negative values than positives under a directional binomial test. As regards issue (2), we expect a negative correlation: a codon strongly preferred in ESE should be relatively strongly enriched near a boundary, hence a big difference in the slope of the codon usage near the boundary. We compute an overall P value combining the P values of the two tests using Fisher’s method to generate a chi squared value, with 2 degrees of freedom. Those indicated in bold are significant after Bonferonni correction (P <0.05/9).