Just when you think you understand how a gene works…BAM! Alternative splicing shows up and reminds us that there is so much yet to learn, even about a gene as well-studied as formin. Genes get transcribed into RNA, which gets translated into proteins. After transcription of a gene, different regions of RNA called exons and introns are either connected together (exons) or removed (introns) in a process called splicing. Some genes undergo a process called “alternative splicing” that allows one single gene the ability to splice, or connect, the exons in multiple ways that result in different protein isoforms. A recent paper describes a previously-unidentified isoform of FHOD3 formin, an actin-nucleating protein found at high levels in the heart. This new isoform includes an alternative exon in certain muscle tissues, and this exon contains a phosphorylation site that allows an additional level of regulation of FHOD3. Images above are of neonatal rat heart cells with or without this alternative exon. The presence of the alternative exon (bottom cell) directs formin (left images, green in merged) to myofibrils (middle images, red in merged), which are the repetitive and contractile structures in muscle cells. Without the alternative exon, formin is found in aggregates in the cytoplasm (top cell).
Iskratsch, T., Lange, S., Dwyer, J., Kho, A., Remedios, C., & Ehler, E. (2010). Formin follows function: a muscle-specific isoform of FHOD3 is regulated by CK2 phosphorylation and promotes myofibril maintenance originally published in The Journal of Cell Biology, 191 (6), 1159-1172 DOI: 10.1083/jcb.201005060
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