Just a brief post this week. A recent paper (Miyamoto et al.) points to a requirement for nuclear actin polymerization during oocyte reprogramming by the transcription factor Oct4. The authors had noticed an enrichment of nuclear actin-regulatory proteins in their analysis of proteins that enhance reprogramming in Xenopus oocytes. To examine the role of actin further, they transplanted mouse nuclei into Xenopus oocytes and, using a probe to visualize filamentous actin, found that there was a large amount of actin polymerization in the nuclei. Blocking actin polymerization by a variety of methods interfered with reprogramming stimulated by the pluripotency factor Oct4. What regulates actin polymerization in the nucleus? The authors focused on actin nucleators described to be present in the nucleus and found that Toca-1 overexpression enhanced Oct4’s activity. Nuclear actin is known to be important in chromatin remodeling and this function might be how it affects Oct4-dependent reprogramming.
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