Table 2.

Effects of a downstream 5′SS or ESE sequences on recruitment of 3′SS components.

	mEGFP‐U2AF65	mCherry‐U2AF35	mEGFP‐U2B′′
BGSMN2	10	12	10
BGSMN2‐ESEx4	16	25	25
BGSMN2‐U1	14	20	27

Values show the percentage of pre‐mRNA molecules in each single‐molecule experiment colocalized with labelled U2AF and U2 snRNP, as indicated. The two components of U2AF were co‐expressed and measurements made in the same experiment; mEGFP‐U2B′′ was expressed separately (Chen et al, 2017). BGSMN2‐ESEx4 is BGSMN2 with a 3′ extension containing four repeats of the enhancer used in BGSMN2‐ESE (Fig 4A). The data for this and BGSMN2 are from Jobbins et al, (2018). The data for BGSMN2‐U1 are shown in Appendix Fig S7. For each of the two extracts, the experiments with all three pre‐mRNA substrates were done at the same time in the same nuclear extract.