LAUSR

The factor responsible for autoregulation of tubulin RNA stability is identified One of the first discoveries of gene expression mediated by controlling messenger RNA (mRNA) stability is autoregulation of tubulin synthesis. In this regulatory process, the concentration of tubulin subunits modulates the stability of the mRNAs from which they are translated (1, 2). In the 1980s it was found that only translated tubulin mRNAs are autoregulated (3) and that translation had to continue through at least 41 amino acids (4). This is enough for the nascent tubulin polypeptide to emerge from the ribosome (5). Later work established that when the tubulin subunit pool is high, the first four amino acids (Met-Arg-Glu-Ile, MREI) emerging during nascent tubulin translation serve as a regulatory tag. Recognition of this tag promoted the degradation of the translating tubulin mRNA (4, 6–8). More than 30 years later, on page 100 of this issue, Lin et al. (9) identify tetratricopeptide repeat protein 5 (TTC5) as the regulator that binds to nascent tubulin polypeptides.