As mentioned in the “Domains of Sbp1 bind to the 5′UTRPab1 cooperatively” section, the Kd of Sbp1 to the 5′UTRPab1 is 26.5 ± 1.1 nM. Under the same experimental conditions, including ionic strength of binding buffers, the Kd of Pab1 to the 5′UTRPab1 is 31.2 ± 2.5 nM (Supplemental Fig. S3). These results show that Sbp1 and Pab1 bind to the A-rich region in the 5′UTRPab1 with a similar affinity in vitro.