Microtubules, built from heterodimers of α- and β-tubulins, control cell shape, mediate intracellular transport, and power cell division. The concentration of αβ-tubulins is tightly controlled through a posttranscriptional mechanism involving selective and regulated degradation of tubulin-encoding mRNAs. Degradation is initiated by TTC5, which recognizes tubulin-synthesizing ribosomes and recruits downstream effectors to trigger mRNA deadenylation. Here, we investigate how cells regulate TTC5 activity. Biochemical and structural proteomic approaches reveal that under normal conditions, soluble αβ-tubulins bind to and sequester TTC5, preventing it from engaging nascent tubulins at translating ribosomes. We identify the flexible C-terminal tail of TTC5 as a molecular switch, toggling between soluble αβ-tubulin-bound and nascent tubulin-bound states. Loss of sequestration by soluble αβ-tubulins constitutively activates TTC5, leading to diminished tubulin mRNA levels and compromised microtubule-dependent chromosome segregation during cell division. Our findings provide a paradigm for how cells regulate the activity of a specificity factor to adapt posttranscriptional regulation of gene expression to cellular needs.
- MeSH
- lidé MeSH
- messenger RNA * metabolismus genetika MeSH
- mikrotubuly * metabolismus MeSH
- proteiny asociované s mikrotubuly metabolismus genetika MeSH
- ribozomy metabolismus MeSH
- segregace chromozomů MeSH
- stabilita RNA * MeSH
- tubulin * metabolismus genetika MeSH
- vazba proteinů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- messenger RNA * MeSH
- proteiny asociované s mikrotubuly MeSH
- tubulin * MeSH
