In type II splicing
1
a 'G-OH' from outside makes a nucleophilic attack on 5'P of first base of intron
2
a free 2'O of an internal adenosine makes a nucleophilic attack on 5'P of first base of intron
3
A 3'O of an internal adenosine makes a nucleophilic attack on 5'P of first base of intron
4
the hydrolysis of last base of exon is carried out by U2/U4/U6