Rcc. Chan et Dl. Black, THE POLYPYRIMIDINE TRACT BINDING-PROTEIN BINDS UPSTREAM OF NEURAL CELL-SPECIFIC C-SRC EXON N1 TO REPRESS THE SPLICING OF THE INTRON DOWNSTREAM, Molecular and cellular biology, 17(8), 1997, pp. 4667-4676
The neural cell-specific N1 exon of the c-src pre-mRNA is both negativ
ely regulated in nonneural cells and positively regulated in neurons.
We previously identified conserved intronic elements Banking N1 that d
irect the repression of N1 splicing in a nonneural HeLa cell extract.
The upstream repressor elements are located within the polypyrimidine
tract of the N1 exon 3' splice site. A short RNA containing this 3' sp
lice site sequence can sequester trans-acting factors in the HeLa extr
act to allow splicing of N1. We now show that these upstream repressor
elements specifically interact with the polypyrimidine tract binding
protein (PTB). Mutations in the polypyrimidine tract reduce both PTB b
inding and the ability of the competitor RNA to derepress splicing. Mo
reover, purified PTB protein restores the repression of N1 splicing in
an extract derepressed by a competitor RNA. In this system, the PTB p
rotein is acting across the N1 exon to regulate the splicing of N1 to
the downstream exon 4. This mechanism is in contrast to other cases of
splicing regulation by PTB, in which the protein represses the splice
site to which it binds.