CONICET | Buscador de Institutos y Recursos Humanos

Changes in transcriptional elongation rate modulate alternative splicing choices. We investigated a physiological role for this mechanism analyzing how chromatin changes associated to neuronal activity affect alternative splicing of the NCAM exon 18. We determined that E18 inclusion decreases upon high K+-induced depolarization in both cultured neurons and N2a neuroblastoma cells. Depolarization also causes general histone hyperacetylation, paralleled with increased levels of histone acetyl-transferases such as CREB-Binding Protein (CBP). Analysis of intragenic chromatin across the NCAM locus revealed low levels of marks associated with active transcription, such as H3K36 tri-methylation and H3K9 acetylation, in the neighbourhood of exon 18. Depolarization causes increased acetylation in that region, chromatin relaxation and increased RNA pol processivity. Using mutant polymerases, we determined that E18 inclusion is responsive to elongation rate, which hints at a influence of transcription in the alternative splicing regulation. Furthermore, histone hyperactetylation induced by Trichostatin A potentiated and even duplicated the depolarization effect, suggesting that changes in the chromatin structure can either facilitate or directly modulate alternative splicing regulation. These experiments point at a physiological role of intragenic chromatin modulation in mRNA biogenesis.