Nuclear actin is required for transcription during Drosophila oogenesis
Actin influences gene expression at multiple levels. It regulates the activity of specific transcription factors, such as myocardin-related transcription factor (MRTF), is a component of many chromatin remodelers and linked to transcription by all three RNA polymerases (Pol). However, the molecular mechanisms by which actin participates in the gene-specific vs. general transcription have remained unclear. Here we use chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) in Drosophila ovaries to demonstrate that binding of actin to the Act5C gene is not dependent on the Mrtf transcription cofactor. At the genome-wide level, actin interacts with essentially all transcribed genes and co-occupies most gene promoters together with Pol II. On highly expressed genes, actin and Pol II can be found also on the gene bodies. Manipulation of nuclear transport factors for actin leads to decreased expression of egg shell genes, demonstrating the in vivo relevance of balanced nucleo-cytoplasmic shuttling of actin for transcription.