Poly(A) tail-length assays were performed on total RNA isolated from the indicated HEK T-REx cell lines in control conditions or after 3 h 100 nM CA4 treatment to induce tubulin autoregulation. Total mRNAs were modified at their 3 ends with a guanosine/inosine tail (G/I tail), reverse transcribed, and PCR amplified using a gene-specific forward primer to either TUBA1B (left) or GAPDH (right) and universal reverse primer. Size markers for PCR products lacking a poly(A) tail were generated using gene-specific reverse primers that anneal in the 3 UTRs 70 nt upstream of the poly(A)-site (first lane of each gel, marked by triangles). PCR products were separated on agarose gels and inverted images are shown. Diagram depicts the PCR strategy and positions of primers. See also Figure S7.
