Heterogeneous nuclear ribonucleoprotein F/H proteins modulate the alternative splicing of the apoptotic mediator Bcl-x.
Bcl-x is a member of the Bcl-2 family of proteins that are key regulators of apoptosis. The Bcl-x pre-mRNA is alternatively spliced to yield Bcl-x(S) and Bcl-x(L), two isoforms that have been associated, respectively, with the promotion and the prevention of apoptosis. We have investigated some of the elements and factors involved in the production of these two splice variants. Deletion mutagenesis using a human Bcl-x minigene identifies two regions in exon 2 that modulate Bcl-x 5'-splice site selection in human HeLa cells. One region (B3) is located upstream of the Bcl-x(L) 5'-splice site and enforces Bcl-x(L) production in cells and splicing extracts. The other region (B2) is located immediately downstream of the 5'-splice site of Bcl-x(S) and favors Bcl-x(S) production in vivo and in vitro. A 30-nucleotide G-rich element (B2G) is responsible for the activity of the B2 element. We show that recombinant heterogeneous nuclear ribonucleoprotein (hnRNP) F and H proteins bind to B2G, and mutating the G stretches abolishes binding. Moreover, the addition of hnRNP F to a HeLa extract improved the production of the Bcl-x(S) variant in a manner that was dependent on the integrity of the G stretches in B2G. Consistent with the in vitro results, small interfering RNA-mediated RNA interference targeting hnRNP F and H decreased the Bcl-x(S)/Bcl-x(L) ratio of plasmid-derived and endogenously produced Bcl-x transcripts. Our results document a positive role for the hnRNP F/H proteins in the production of the proapoptotic regulator Bcl-x(S.).
Garneau
Daniel
D
RNA/RNP Group, Département de microbiologie et d'infectiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Québec, Canada.
Revil
Timothée
T
Fisette
Jean-François
JF
Chabot
Benoit
B
D017398:Alternative Splicing; D017209:Apoptosis; D015153:Blotting, Western; D018076:DNA, Complementary / Q000378:metabolism; D005091:Exons; D017353:Gene Deletion; D006367:HeLa Cells; D034541:Heterogeneous-Nuclear Ribonucleoprotein Group F-H / Q000737:chemistry*; D006801:Humans; D016297:Mutagenesis, Site-Directed; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry* / Q000235:genetics*; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D014162:Transfection; D051020:bcl-X Protein
C494811:BCL2L1 protein, human; D018076:DNA, Complementary; D034541:Heterogeneous-Nuclear Ribonucleoprotein Group F-H; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D051020:bcl-X Protein