TABLE 1.

Potential base pairing of the G1 and G2 elements with the U1 snRNAs used in this study

Base pairinga	RNAb	ΔGc (kcal/mol)	Figured
5′ G G G C C G G G 3′	Wt G1	−1.5	7C(1)
·····
3′ U C C A U U C A U A 5′	Wt U1
5′ G G G U C G A G G G G 3′	Wt G2	−3.1	7C(1)
······
3′ U C C A U U C A U A 5′	Wt U1
5′ U G A C C A G C 3′	Mutant G1	>0	7C(2), 7E(1), 8B(2)
···
3′ U C C A U U C A U A 5′	Wt U1
5′ A G C U C G A U G C G 3′	Mutant G2	>0	7C(2 and 6), 7D (plot)
······
3′ U C C A U U C A U A 5′	Wt U1
5′ U G A C C A G C 3′	Mutant G1	−12.6	7C(4), 8B(3)
········
3′ A C U G G U C G A 5′	G1MutAS U1
5′ U G A C C A G C 3′	Mutant G1	−1.3	7D (plot)
·····
3′ A C U A U U C A U A 5′	G1-1 rescue U1
5′ A G C U C G A U G C G 3′	Mutant G2	−18.1	7E(5 and 8)
···········
3′ U C G A G C U A C G C A 5′	G2MutAS U1

^aAligned to allow for base pairing (periods) between U1 nucleotides 8 to 10 and a GGG element. Potential base pairing of the G1 and G2 elements with U1 nucleotides in addition to 8 to 10 is also indicated. Experimental evidence, however, indicated that these positions are not essential for the interaction of the wild-type elements with U1 (Fig. 4). 

^bIdentity of each G element and U1 snRNA. Wt, wild type. 

^cΔG values were calculated as described previously (13). 

^dFigure and lane numbers (in parentheses) where the indicated element and U1 combination analyzed for in vivo effects on splicing are shown.