Dual regulation of coronin-1 expression by the core promoter and intronic regions

Coronin family proteins are involved in various cellular processes, such as actin cytoskeleton reorganization, cell motility, and vesicular trafficking. Coronin-1, encoded by Coro1a, is specifically expressed in immune cells, and its defect causes severe immunodeficiencies. However, the regulatory mechanisms of Coro1a expression in immune cells remain unknown. Here, we aimed to elucidate the regulatory mechanisms of Coro1a expression. A reporter assay revealed that the promoter region alone was insufficient for Coro1a transcription; both the promoter and gene body regions were required. Promoter deletion analysis revealed that the 85-base fragment of the 5'-flanking region is required for Coro1a transcription in RAW264.7 cells. We identified 5 consensus sequences of GC boxes within this region, and the Sp3 transcription factor was found to bind to the GC box 4 most involved in coronin-1 expression. Sp3 binding regulation likely depended on chromatin accessibility. Further, DNase sequencing analysis revealed several open chromatin regions in the gene body region, including introns, in immune cells. Higher levels of active histone modifications, H3K4me3 and H3K27ac, were also detected in the gene body regions. Five ETS-binding sequences existed in introns 1 and 2, and mutations at these sequences decreased Coro1a transcription. Furthermore, active histone modifications at the intronic region were decreased during differentiation of bone marrow-derived macrophages into bone marrow-derived osteoclasts, which was accompanied by a reduction in Coro1a expression. These results demonstrate that Coro1a transcription is regulated by both the promoter and intronic regions, and this dual regulation could be important for Coro1a transcription in immune cells.