passages.id: split_4_test_227_passage
passages.type: progene_text
passages.text: Cross - linking studies with pre - mRNAs containing the 5' ss or BPS alone indicate that recognition of the BPS by the U12 snRNP is stimulated at least 20 - to 30 - fold by the binding of the U11 snRNP to the 5' ss in the same pre - mRNA molecule , whereas recognition of the 5' ss by U11 is stimulated approximately fivefold by the U12 / BPS interaction .