miRNA-145 represses Klf-4, Oct4 and Sox2, and is repressed by Oct4How pluripotency is controlled is one of biology's major puzzles. New research led by Kenneth Kosik of the University of California, Santa Barbara reveals not only a new piece in the puzzle but also how some major pieces fit together.A set of transcription factors — Klf4, Oct4 and Sox2 — is sufficient to reprogram specialized cells to pluripotency. As pluripotent cells take on a differentiated fate, these transcription factors disappear. Kosik found that one microRNA (miRNA) is able to repress all three of these proteins.Although these small RNA molecules can...