RPS6KA3 and colorectal cancer: A high‐throughput strategy for identifying functional phosphorylation sites involved in 5‐fluorouracil (5‐FU) resistance is introduced using clustered regularly interspaced short palindromic repeats (CRISPR)‐mediated cytosine base editor (CBE) and adenine base editor (ABE), by mutating phosphorylated amino acids with guide RNA libraries, and RSK2 and PAK4 kinases are identified as main effectors in responding to 5‐FU chemotherapy for colorectal cancer.