Spi-1/PU.1 oncoprotein affects splicing decisions in a promoter binding-dependent manner.
The expression of the Spi-1/PU.1 transcription factor is tightly regulated as a function of the hematopoietic lineage. It is required for myeloid and B lymphoid differentiation. When overexpressed in mice, Spi-1 is associated with the emergence of transformed proerythroblasts unable to differentiate. In the course of a project undertaken to characterize the oncogenic function of Spi-1, we found that Spi-1 interacts with proteins of the spliceosome in Spi-1-transformed proerythroblasts and participates in alternative splice site selection. Because Spi-1 is a transcription factor, it could be hypothesized that these two functions are coordinated. Here, we have developed a system allowing the characterization of transcription and splicing from a single target. It is shown that Spi-1 is able to regulate alternative splicing of a pre-mRNA for a gene whose transcription it regulates. Using a combination of Spi-1 mutants and Spi-1-dependent promoters, we demonstrate that Spi-1 must bind and transactivate a given promoter to favor the use of the proximal 5' alternative site. This establishes that Spi-1 affects splicing decisions in a promoter binding-dependent manner. These results provide new insight into how Spi-1 may act in the blockage of differentiation by demonstrating that it can deregulate gene expression and also modify the nature of the products generated from target genes.
Guillouf
Christel
C
Institut Curie, INSERM U528, Paris 75248, France. guillouf.christel@curie.fr
Gallais
Isabelle
I
Moreau-Gachelin
Françoise
F
D017398:Alternative Splicing; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C486039:SPIC protein, human