TIA-1 and TIAR activate splicing of alternative exons with weak 5' splice sites followed by a U-rich stretch on their own pre-mRNAs.
TIA-1 has recently been shown to activate splicing of specific pre-mRNAs transcribed from transiently transfected minigenes, and of some 5' splice sites in vitro, but has not been shown to activate splicing of any endogenous pre-mRNA. We show here that overexpression of TIA-1 or the related protein TIAR has little effect on splicing of several endogenous pre-mRNAs containing alternative exons, but markedly activates splicing of some normally rarely used alternative exons on the TIA-1 and TIAR pre-mRNAs. These exons have weak 5' splice sites followed by U-rich stretches. When the U-rich stretch following the 5' splice site of a TIA-1 alternative exon was deleted, TIAR overexpression induced use of a cryptic 5' splice site also followed by a U-rich stretch in place of the original splice site. Using in vitro splicing assays, we have shown that TIA-1 is directly involved in activating the 5' splice sites of the TIAR alternative exons. Activation requires a downstream U-rich stretch of at least 10 residues. Our results confirm that TIA-1 activates 5' splice sites followed by U-rich sequences and show that TIAR exerts a similar activity. They suggest that both proteins may autoregulate their expression at the level of splicing.
Le Guiner
C
C
INSERM U463, Institut de Biologie-CHR, 9 Quai Moncousu, 44093 Nantes Cedex 1, France.
Lejeune
F
F
Galiana
D
D
Kister
L
L
Breathnach
R
R
Stévenin
J
J
Del Gatto-Konczak
F
F
D017398:Alternative Splicing / Q000502:physiology*; D001483:Base Sequence; D005091:Exons; D005786:Gene Expression Regulation / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000502:physiology*; D008969:Molecular Sequence Data; D039102:Poly(A)-Binding Proteins; D011506:Proteins; D012322:RNA Precursors / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000074019:T-Cell Intracellular Antigen-1
D008565:Membrane Proteins; D039102:Poly(A)-Binding Proteins; D011506:Proteins; D012322:RNA Precursors; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D000074019:T-Cell Intracellular Antigen-1; C071558:TIA1 protein, human; C076751:TIAL1 protein, human