Control of alternative splicing through siRNA-mediated transcriptional gene silencing

MARIANO ALLÓ; VALERIA BUGGIANO; JUAN PABLO FEDEDA; EZEQUIEL PETRILLO; IGNACIO SCHOR; MANUEL DE LA MATA; ENERITZ AGIRRE; MIREYA PLASS; EDUARDO EYRAS; SHERIF ABOU ELELA; ROSCOE KLINCK; BENOIT CHABOT; ALBERTO RODOLFO KORNBLIHTT

NATURE STRUCTURAL & MOLECULAR BIOLOGY

NATURE PUBLISHING GROUP

Año: 2009 p. 717 - 725

1545-9985

When targeting promoter regions, small interfering RNAs (siRNAs)trigger a previously proposed pathway known as transcriptional gene silencing by promoting heterochromatinformation. Here we show that siRNAs targeting intronic or exonic sequences close to an alternative exon regulatethe splicing of that exon. The effect occurred in hepatoma and HeLa cells with siRNA antisense strands designedto enter the silencing pathway, suggesting hybridization with nascent pre-mRNA. Unexpectedly, in HeLa cells thesense strands were also effective, suggesting that an endogenous antisense transcript, detectable in HeLa butnot in hepatoma cells, acts as a target. The effect depends on Argonaute-1 and is counterbalanced by factorsfavoring chromatin opening or transcriptional elongation. The increase in heterochromatin marks (dimethylation atLys9 and trimethylation at Lys27 of histone H3) at the target site, the need for the heterochromatin-associated proteinHP1a and the reduction in RNA polymerase II processivity suggest a mechanism involving the kinetic coupling oftranscription and alternative splicing.