HP1gamma Knock Down in Human cells

Study of HP1 Knock Down on gene expression and splicing regulation in Human HeLa cells Maturation of pre-mRNAs is initiated co-transcriptionally. It is therefore conceivable that chromatin-borne information participates in alternative splicing. Here, we find that elevated levels of tri-methylation of histone H3 on lysine 9 (H3K9me3) are a characteristic of the alternative exons of several genes including CD44. On this gene, the chromodomain protein HP1gamma, frequently defined as a transcriptional repressor, facilitates inclusion of the alternative exons via a mechanism involving decreased RNA polymerase II elongation rate. In addition, accumulation of HP1gamma on the variant region of the CD44 gene stabilizes association of the pre-mRNA with the chromatin. Altogether, our data provide evidence for localized histone modifications impacting alternative splicing. They further implicate HP1gamma as a possible bridging molecule between the chromatin and the maturating mRNA, with a general impact on splicing decisions. Transcriptome analysis of siRNA anti-HP1gamma transfected HeLa cells on GeneChip® Human Exon 1.0 ST Arrays (Affymetrix). Control HeLa cells have been transfected with the same concentration of siRNA anti-GAPDH. Experiment has been done in experimental triplicates.