Targeted snRNP depletion reveals an additional role for mammalian U1 snRNP in spliceosome assembly

HeLa cell nuclear splicing extracts have been prepared that are specifically and efficiently depleted of U1, U2, or U4/U6 snRNPs by antisense affinity chromatography using biotinylated 2'-OMe RNA oligonucleotides. Removal of each snRNP particle prevents pre-mRNA splicing but arrests spliceosome formation at different stages of assembly. Mixing extracts depleted for different snRNP particles restores formation of functional splicing complexes. Specific binding of factors to the 3' splice site region is still detected in snRNP-depleted extracts. Depletion of U1 snRNP impairs stable binding of U2 snRNP to the pre-mRNA branch site. This role of U1 snRNP in promoting stable preslicing complex formation is independent of the U1 snRNA-5' splice site interaction.     

Exonic splicing enhancers: mechanism of action, diversity and role in human genetic diseases

Exonic splicing enhancers (ESEs) are discrete sequences within exons that promote both constitutive and regulated splicing. The precise mechanism by which ESEs facilitate the assembly of splicing complexes has been controversial. However, recent studies have provided insights into this question and have led to a new model for ESE function. Other recent work has suggested that ESEs are comprised of diverse sequences and occur frequently within exons. Ominously, these latter studies predict that many human genetic diseases linked to mutations within exons might be caused by the inactivation of ESEs.     

Stabilization of Peptide-Based Vesicles via in situ Oxygen-Mediated Cross-Linking

Reversible vesicles from poly(L-glutamic acid)(65) -block-poly[(L-lysine)-ran-(L-3,4-dihydroxyphenylalanine)](75) [PLGA(65) -b-P(LL-r-DOPA)(75) ] block copolypeptide adopt different configurations depending on the surrounding pH. At pH?=?3, AFM and TEM images show ellipsoidal morphologies, whereas at pH?=?12 both TEM and AFM reveal the formation of hollow vesicles. At pH?=?12, the P(LL-r-DOPA) block forms the internal layer of the vesicle shell and the subsequent oxygen-mediated oxidation of the phenolic groups of the DOPA lead to the formation of quinonic intermediates, which undergo intermolecular dimerization to stabilize the vesicles via in situ cross-linking. Consequently, the vesicles maintain their shape even when the pH is reversed back to 3, as confirmed by AFM and TEM.