Table I.

Up to 86% of the Sh1 first intron can be deleted without affecting the enhancement of gene expression

Construct	CAT Activity		Intron	Splicing Efficiencya
	Mean	Range	AT	Mean	Range
	%		%
DEL1	134.4	94.0–174.7	57.5	71.2	64.4–77.0
DEL2	40.8	30.8–50.8	51.9	20.8b	16.9–27.5
DEL3	24.3	13.6–35.0	48.6	17.7b	11.4–26.8
DEL4	87.7	82.6–92.8	60.6	65.1	41.3–77.0
DEL5	89.4	57.6–121.3	61.2	47.9	38.7–59.2
DEL6a	168.5	98.7–238.2	61.8	69.0	64.4–75.4
DEL7	82.7	59.9–105.5	58.6	53.1	46.0–70.5
DEL8	32.5	27.6–37.4	54.5	50.9	44.5–55.4
DEL9	40.7	40.4–41.0	53.3	55.3	52.5–57.6
DEL10	11.3	10.1–12.5	51.4	42.3	34.4–42.5
DEL11	4.6	2.3–6.8	47.5	0c	–

Enzyme extracts were prepared 45 h post-transfection in one experiment and at 24 h in a second experiment. CAT activity is given relative to construct 35SIfSCN, which contains the entire Sh1 first intron, and is the result of the two determinations. In the same two experiments, RNA was prepared at both 1 and 2 d post-bombardment. Transcript splicing efficiency is the result of the four measurements.

^aSplicing efficiency = percentage of transcripts correctly spliced. 

^bAlternatively spliced transcripts also produced. 

^cOnly unspliced transcripts were detected.