I found part of the answer why hnRNP needed in RNA splicing (to cut intro exon).
Because hnRNP A2 on RNA will use kinesin on microtubule to move it self. (supported by this paper)
and this paper also support my theory
so it can move two splicesome together (my theory).

this paper support my another theory, "a novel class of genes which, although they encode polyadenylated RNA, might not make a translated protein."

this abstract also support my third theory, when enzyme see the sequence, they don't know if they cut the right place or not, they just cut it. There's other place to check if they cut right or not.

and I'll use these three theory in my binf7600 project.

and this one should be able to help me to detect hnRNP binding site.

(I found this on 10/10/03, which draw exactly as I thought! and support all my theory!)