Identification, purification, and biochemical characterization of U2 small nuclear ribonucleoprotein auxiliary factor.

摘要: Binding of U2 small nuclear ribonucleoprotein (snRNP) to the pre-mRNA branch site is an early step in spliceosome assembly and appears commit a splicing pathway. We have shown previously that this ATP-dependent binding requires non-rnRNP factor, snRNP auxiliary factor (U2AF), addition snRNP. In report we identified U2AF, purified it homogeneity, characterized its biochemical properties. Purified U2AF comprises roughly equimolar quantities two polypeptides, approximately 65 kDa 35 kDa, which appear be associated. Measured by ultraviolet crosslinking, 65-kDa polypeptide binds specifically polypyrimidine tract/3' splice region. rapidly at 4 degrees C absence ATP remains associated with following binding. Thus, simple initiates mammalian facilitating