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BIOGRAPHY:
Dr. Kornblihtt received a Ph.D. in biochemistry in 1980 from the University of Buenos Aires, Argentina. He conducted postdoctoral studies in the United Kingdom at the Sir William Dunn School of Pathology, University of Oxford. He has received the Bernardo Houssay Prize from the National Research Council of Argentina, a Guggenheim Fellowship, and in 2000 was awarded the Antorchas Fellowship. He currently holds the position of Professor in the Facultad de Ciencias Exactas y Naturales of the University of Buenos Aires. His HHMI-funded project involves mechanisms of coupling between transcription and alternative mRNA splicing in human cells.
RESEARCH ABSTRACT SUMMARY:
Control of Alternative Splicing by RNA pol II Elongation
Alternative splicing (AS) is a major contributor to proteome
diversity in metazoans. AS of the fibronectin extra domain I (EDI) exon
is controlled by RNA polymerase II (pol II) elongation and by the
binding of the splicing factor SF2/ASF to an exonic splicing enhancer
(ESE) present in EDI. Faster elongation rates elicit higher exon
skipping according to a model where skipping occurs because the 3′
splice site (ss) of the upstream intron is suboptimal compared with the
3′ss of the downstream intron. We tested the model in cis, by
strengthening the suboptimal 3′ss, and in trans, by looking at
AS when transcription is performed by a "slow" pol II
mutant. We found that the better the exon is recognized by the splicing
machinery, the less its splicing is affected by pol II elongation
(Nogués et al., J. Biol. Chem. 278:52166–52171, 2003) and
that transcription by a "slow" polymerase not only inhibits
EDI skipping but also affects alternative splicing of other genes such
as adenovirus E1a and Drosophila's Ultrabithorax (de la
Mata et al., Mol. Cell 12:525–532, 2003).
We prepared minigenes with two EDI regions arranged in tandem under
a single promoter. We found that the proximal AS event influences the
distal one: disruption of the ESE at the proximal EDI not only prevents
its own inclusion but favors skipping of a wild-type distal EDI exon.
The effect is polar in nature because disruption of the distal EDI ESE
does not affect skipping of the proximal one, which suggests a strong
link with transcription.
The human transcriptional coactivator CA150 was reported to decrease
transcriptional elongation by interacting with pol II carboxy-terminal
domain. Consistent with our model, overexpression of CA150 provokes a
fourfold increase in EDI inclusion. Paradoxically, reduction in
endogenous levels of CA150 by RNA interference also increases EDI
inclusion, indicating dual roles for this coactivator.
Photo: Dominic Chaplin, Pine Creek Pictures
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