In mammals actin contributes to transcription elongation by facilitating establishment of permissive chromatin. Here we report that the F-actin severing protein cofilin-1 is part of the same complex with actin and phosphorylated RNA polymerase (pol) II. In chromatin immunoprecipitation assays cofilin-1 was found selectively associated with transcribed regions of active genes, its occupancy being influenced by the polymerization state of actin. Cofilin-1 gene silencing led to a drop in FUrd incorporation into nascent transcripts. In cofilin-1 silenced cells chromatin immunoprecipitations showed that active genes were devoid of actin, phosphorylated pol II and displayed low histone H3 acetylation levels on K9. These findings suggest that cofilin-1 plays a major role in pol II transcription, facilitating association of elongating pol II and actin with active genes. We speculate that cofilin-1 performs its function in pol II transcription by regulating polymerization of gene-associated actin.
Keywords: RNA polymerase II; cofilin; nascent mRNA; nuclear actin; transcription elongation.