PMC

Relative ratio of PTB and nPTB expression during cell differentiation.

Models of RNA-PTB interaction in exon splicing repression. (A) Repression by PTB looping out a branch-point adenosine; (B) PTB monomer looping-out an exon; (C) Multiple PTB molecules binding cooperatively around an alternative exon; (D) PTB cooperates with the co-factor Raver1 to loop out an alternative exon by binding to distant intronic pyrimidine tracts.

RNA binding proteins are involved in all steps of RNA biogenesis. Starting from pre-mRNA transcript synthesis, a variety of different RNA binding proteins are associated within the heterogeneous ribonucleoprotein complexes, participating in the processes which result in the formation of mature mRNA, including pre-mRNA splicing and addition of 3′ poly(A) tails in the nucleus and mRNA export through the nuclear pores. In the cytoplasm, they participate in localization, initiation of translation, and mRNA stability.

PTB RRM3 structure. (A) The PTB RRM3 structure was obtained with Swiss-PdbViewer (http://www.expasy.org/spdbv/); (B) Alignments of ribonucleoprotein (RNP) 2 and RNP1 sequences present in the PTB RRM3 with RRM containing proteins. The alignment was generated by ClustalW and manually optimized. PTB, polypryrimidine tract binding protein; nPTB, neuronal PTB; hnRNPA1, heterogeneous nuclear ribonucleoprotein type A1; LA, La protein; TAP, mRNA export factor Tap; PABP, Poly(A)-binding protein; CSTF64, cleavage stimulation factor 64; Y14, Y14 Magoh complex; HUD, Hu protein; SXL, Sex-Lethal; U1A, U2B, U1 snRNP proteins; CBP20, cap-binding protein 20; UPF3, up-frameshift protein 3; U2AF65, U2 snRNP auxiliary factor; RBM20, RNA binding motif 20.